First of all, the Jaguar is not the best console of it's time. You might be better off getting a 3DO, N64, or PSX. However, if you do have this, there are some very good games for it, although the library certainly isn't as memorable as some other fifth-generation consoles.
Probably the best game on the console. First of all, this soundtrack is pure awesome. In fact, the soundtrack was even released as a CD.
You play as a ship, fixed on the edge of a colorful "web" and you shoot incoming shit and get powerups. Very addictive.
Alien vs. Predator
Play as an Alien rescuing the Alien queen, a predator trying to kill the Alien queen, or as a marine trying to get the fuck out of there.
Marine campaign is by far the best, although all three of the campaigns are good.
A must-have for the Jaguar.
Basically you control a squad of soldiers, and you have to complete the objective of a mission, divided into phases.
Whoever survives the mission gets a promotion and becomes a bit better.
Missions get pretty complex and require some creative thinking later on.