Well, GURPS Basic 4th, easy choice. Best RPG ever made. An improvement over the 3rd edition.
A small improvement. I'd take the new Ars Magica next, and The Authority next by default, even though I've never even seen it. I don't think the D&D Basic Set should even be considered as it's a reduced repackaging of the full D&D game, and I hate World of Darkness. Too much whining, too little roleplaying.
This, folks, is a really pathetic list. We have three upgrades of venerable industry stalwarts, and a reduced version of a fourth (and really, the D&D Basic Game shouldn't count, not even being a new version, but rather different packaging). And though superhero games are not my cup of tea (the closest I ever come is Epic D&D, which has always struck me as being very superheroesy), I really wouldn't mind if The Authority won, being as that it the only actually new game on the list.