The Neo Geo Pocket Color is entirely backwards compatible with Neo Geo Pocket games, but most people don't realize that if you REALLY can't get your hands on a NGPC, the Neo Geo Pocket could play ALMOST any color game, just not in color. A few exceptions, like Match of the Millennium, actually had some hidden pictures or other silly little extras if you tried a reversal play. Not that NGPC are rare, they're easier to find than a NGP...
Oh and you can hook up your NGPC to a DC for other goodies.
Baseball Stars Color
A rookie-version of the console veterans. The only thing really lost here are the facial expressions of the characters, though they still emote quite a bit. You can still make custom teams, and even unlock other players. It even controls surprisingly well! Probably best fun played with another.
Big Bang Pro Wrestling
Fighting / Sports
A pretty neat wrestling game. It's no Saturday Night Slam Masters, but honestly, it's probably the closest you'll get to it on a retro portable. Has a variety of wrestlers with different skills and intros. It's a bit challenging to learn, but once you get the gameplay down, there's much rumbling and many good times to be had.
RPG / Roguelike
Customize your mech, go through randomly generated dungeons to kill critters and find loot, fight in contests. A bit basic compared to later games of the "customizable robot" genres, but the large amount of customization to be found in this early entry is admirable and makes it worth trying out.
Bust A Move! Pocket
It's a portable Bust A Move/Puzzle Bobble with elements from Puzzle Bobble 2. There's really not much else you need to know, other than a vs-cpu and vs. 2-player mode. Just as fun as its console cousins.
Cool Cool Jam
Pretty similar to the Dreamcast game but in 2D and it's a bit more like Beatmania. Nippon Onry!
Can be linked to Cool Cool Toon for goodies.
Cotton: Fantastic Night Dreams
Shoot 'em Up
A horizontal cute 'em up that features a cute witch in a pretty twisted world on a search for candy. Features a variable weapon upgrade system (Kicking ass lets you kick more, while sucking means you'll likely get your ass kicked), and is a pretty close port, despite being scaled down a bit. Kinda hard, but fun. Probably the most expensive NGPC game!
A fun pac-man clone thats much better than the actual port of pac-man for the NGPC. You collect Monster card and stuff to, so theres a collection element to the game.
Dark Arms: Beast Buster 1999
A curious arcade-esque action-RPG. Your character never once levels up, but can collect power-ups in stages. What does level up are your weapons. Capture enemy souls, feed them to your weapons, and evolve them into a variety of cool and twisted things, including, but not limited to: a machine gun that covers your body in steel, tentacle arms, laser cannons, and exploding dolls. You can also change your weapon's affinity, which affects damage done to elemental foes. The day/night cycle also affects your exploration, opening and closing different paths. The only flaw is it's short. Definitely give it a shot though.
Dive Alert: Becky's/Matt's version
It's like Pokemon, but with all the fun of "You sunk my battleship"! Different versions have different stories and ships to use.
More baseball fun
Evolution: Eternal Dungeons
RPG / Roguelike
A port of the Dreamcast RPG. Outside of graphics and music being scaled down a bit, town exploration limited to menus, and the lack of jumping, damn near EVERYTHING from that game can be found in here. The dungeons are still all randomly generated, the battle system works exactly the same, and Cyframe customization is still as neat as ever. If you can't find the Dreamcast version, you'll essentially get the full game (sans any fancy flashiness) in this port. Highly recommended.
A tactics game that has every single action you do revolve around strategy and commands, even turning in a different direction. Despite sounding lame on paper, it actually works quite well. If you're a fan of mecha series, you might also enjoy the atmosphere conveyed in here, which is highly reminiscent of said source material.
A humorous all girl showdown between rough-and-tumble gals from various SNK games. The character selection is a bit small, but you can change some of their properties by equipping different accessories. Everything is well animated, featuring many send-ups of the character's original attacks (though still just as effective). The music's great, and the control is spot on. The big draw here is the option to change game speed, allowing some insanely fast-moving fights, which is loads of fun as a result.
Ganbare Neo Poke-kun
A funny little Wario-Ware like game only all the games are parodies of real games. A satirical look at the history of video-games including everything from Pong to Dragon Warrior to King of the Fighters. Some little sim bits too! (That also happen to be random as hell but very amusing)
Note: Poke-Kun is the NGPC's mascot!
Kikou Seiki Unitron
RPG / Rougelike
The Japan only sequel to Bio Motor Unitron, which expands upon parts and stuff like story which you'd expect, cheaper than the first but good luck if you don't read Japanese!
King of Fighters R-2
A well done mini-remix of King of Fighters '98. Features less characters, but has alternate versions for most fighters, which is cool if you're in the technical know. To make up for the small roster, it features "Making Mode", which is an RPG-esque take on the game, with several abilities to find and equip, and various challenges to face. Also, consider KoF R-1 as a supplement. It lacks the extras this has, but does feature a few characters not in this.
The Last Blade
The original Last Blade games were well-loved for their incredible gameplay, and were a shining example among fighting games. Amazingly, none of that has been lost in this remix. Features spectacular graphics for the NGPC, well done music transitions, and a pretty good cast of characters. One really cool factor is it grows from a mini-LB1 into an LB 1+2 hybrid as you progress with various fighters, and a number of things change in-game. This is great to have, even if you've played the originals. What Match of the Millennium is for many great characters, Last Blade is for great gameplay.
Magical Drop Pocket
Metal Slug: 1st Mission
Run 'n Gun
This remix is not 100% like its console brethren, given the life bar and such, but it's still fun to kick your enemies' asses! There are 3 types of weapons and two types of vehicles to use. It's more straight-forward than the 2nd, but there are some hidden side-stages to access in this one as well. Metal Slug Advance on the Gameboy Advance is the spiritual successor to this mini-series, but plays more like this one (sans bomb switch button). Annoying in that if you want to pause you're probably going to throw a bomb first. Same for below.
Metal Slug: 2nd Mission
Run 'n Gun
Features various weapons, vehicles, music, and gigantic bosses you'd come to expect from the Metal Slug series. However, there are a number of neat aspects added as well. Some stages aren't entirely linear, occasionally you have to do some sneaking missions with a knife only, and each character has a slightly different mission set. While slower stages in a fast paced franchise may sound weird, it works really well. Definitely one of the best entries for the NGPC.
Neo Geo Cup '98 Plus Color
A soccer/football game. Choose a country from teams around the world, each with their own specialties, and go for the gold! A really cool factor here is a slight RPG-esque team player customization. Once you get more money, you can buy gear to improve them. However, many are double-edged, some boosting a stat, while slightly lowering another. Careful consideration and team balance are key! That said, it's neat to see the other little touches, like seeing the announcers and players interlude between goals. It's probably the all-around best sports game on the console.
Ogre Battle Gaiden: The Prince of Zenobia
A side story to the Ogre Battle series. Basically a scaled down March of the Black Queen, and one of the longer NGPC games. It's only in Japanese though.
"Picture Puzzle" my ass. This is Picross. Make pictures by filling in the proper spaces. No American release to my knowledge...
Pocket Tennis Color
It's just like Mario Tennis, you don't have to give two shits about the sport to enjoy this game.
Classic Puyo Puyo on your good ole NGPC.
This is a quirky puzzle game. It has you shooting bridge pieces to connect different color parts in order to clear the stage to get cards of weird monsters. It sounds weird and complicated, but it's actually quite easy and nice fun as well. It gets damn hard on later levels though, so beware. Curiously, the monster cards are kind of funny, but serve no purpose in-game to my knowledge.
Puzzle Link 2
If you liked the first, here's some more. More stages, more shooting, more funny little monster cards.
Rockman Battle & Fighters
Contains pretty good ports of Megaman Power Battle and Megaman Power Fighters. For those not in the know, it's like normal Megaman, but with boss fights only, making it into a fighting game, and much more fast-paced and action-packed.A physical copy is fairly expensive, generally around $100, and emulators for the NGPC are decent but struggle to get the sound right.
Samurai Shodown! 2
A pretty good transition of classic SS action, now cute-ified. Of particular note are character cards, which can slightly improve their stats of power, defense, specials, etc. A similar concept was later used in Metal Slug Advance.
SNK Vs Capcom: Card Fighters Clash (Capcom/SNK Versions)
Hands down one of the best card games of all time. It's most similar to Yu-Gi-Oh, but with far less bullshit and far more balanced. The only truly restricted elements are duplicates (only up to 3 of any card in your deck) and SP needed to use Action cards (like spell cards, they help you or hurt your enemy). Chara-cards may also have special abilities which simulate Action cards and other effects as well. In addition to that, you can dump up to 3 cards into one chara-card (depending on the card) to power it up further (Example: Marco, Fio, Eri, Tarma). There's a whole lot to see and do here, even post-game. The differences between the two are minimal, with some cards being exclusive or hard to find on one versus the other (unless you trade). In short, just choose the one you like, and start collecting and fighting. You don't need to be a hardcore fan of SNK or Capcom to enjoy this, but you may miss out on several of the references made.
SNK Vs Capcom: Card Fighter's Clash 2 (Expand Edition)
Pretty much more of the same that the first game gave you. A new element added is Reaction cards, which act like Yu-Gi-Oh's trap cards, and also require SP. This one lacks a bit of the magic the first had, mostly because the RPG-like world of the first is downplayed and there's far less cool references, but in the end, it's still a good successor to it.
STAY THE FUCK AWAY FROM THE DS GAME THOUGH.
SNK vs. Capcom: Match Of The Millennium
This is why many people owned an NGPC. Outside of the spot-on fighting with different super-mode settings from Capcom and KoF, there's the cool "Olympic" mode. This includes a few mini-games based on a few Capcom and SNK characters and also some fighting-based challenges. The purpose of these is to gain points which unlock new super-attacks for your characters. The sheer combination of characters, stages, music, and bonuses from so many games is enough to make any fighting fanatic salivate. If you've never played a fighting game before, this one would be a great start.
Sonic the Hedgehog: Pocket Adventure
Pretty much a port of Sonic 2 with some elements from Sonic 3 added in. The game controls quite well, and the music sounds pretty good, too. There's a few features as well, like time trials and 2-player racing stages, and collecting puzzle pieces. Only platformer on the system!