1)64-bit-- While there are many arguments about the Jag's power, it is a complete 64-bit system. Not to mention it is the first 64-bit system ever, and came out wayyy before the n64 (Jag's release was in Oct. 1993)
2)Inexpensive-- Right now you can get one for $60. Some places sell less a little less too. Games are also pretty inexpensive ranging from $2 (I've heard) to $60 (for new games). But compared to other systems, you're saving a lot of money, and for better games on most accounts.
3)Not a ton of accessories to buy-- Other systems nowadays have you buying tons of stupid little accessories, like different color controllers, memory paks, and things to make your paddle "shake" (ugh). But with the Jaguar, you have two controllers to chose from: the regular and the Procontroller (an enhanced version of the regular controller. Works much better). And you don't need "controller" or "memory" paks either...the Jaguar can SAVE ONTO IT'S OWN CARTRIDGES!. There is a memory track to buy for the CD's, but it's inexpensive, and one will save data for up to 250 games. It just makes sense...
This is the Jaguar's regular controller. It may look complicated at first, but it's very easy to use and to get used to. The number of buttons allows for tons of combinations to kill your enemies with. Believe me, if my 9 year old brother and his friends can play games with this pad without thinking about it, you can too.
4) Great games - Personally, I think it has more games that are good than it has bad ones. Tempest 2000, Defender 2000, Alien Vs. Predator, Rayman, Iron Soldiers 1 & 2, Doom, Wolfeinstien 3D, Super Burnout, Zero-5, BattleMorph, Worms, Missle Command 3D are ones that instantly come to mind. Not to mention we're getting more games soon. BattleSphere, The Assassin, Age of Darkness, Protector, Group Game(JagDoom 2), Legion Force Jidai, Gorf 2000, Native:Reborn, and maybe Skyhammer are on the list. There's also Band-in-the-Box who's working on some stuff, but I haven't heard about them in a while, and I don't know where their websites at. But, we've got a pretty good future for the Jag if you think about it.