I am ambivilant about Alternity; in some ways I am much happier with the current situation- A.net and all the material we are creating. OTOH, if it still had support there would be many more people working on improving it.
One currently in print game I wish had a lot more fans is vs Monsters and the vsM engine in general. And the same goes for JAGS 13 Colonies, Have-Not and Wonderland.
The Fantasy Trip. It seemed to be catching on really well in the US before the company owner dropped out from society. Too bad Steve Jackson couldn't get the rights back in the day.
Buffy The Vampire Slayer RPG. I always wished Eden had released the cinematic Unisystem variation separately, so non-fans of the show could have fun gaining and burning Drama Points too.
Most of all, I hope that True20 catches on more, so it will be easier to find other players.
Vote Number Three for Torg - I always thought it had the potential for a stupendous game story wise ... as for the mechanics of the game, admittedly I never had the chance to play it! BUT I loved the ... err ... "setting concept"?
It was the first game I ever ran on a regular basis(circa 1983-4). My campaign took place in the star wars universe and lasted about a year. A few years later d6 star wars came out, but by then we'd moved on to something else.
Hands down, the James Bond system. I've never seen rules better matched to a setting. At the same time, you could easily transplant the core mechanic into just about any heroic RPG concept. Flawless.