Calling FFXIII an incredible game is like saying Duke Nuken forever will be Mankind's greatest contribution to Art & Culture (See Yahtzee).
It's not out yet. It won't be out for a long time. And yes, the older versions were mostly good (FFXII for truly pushing PS2 graphically, that's about all the good I can say about it, Duke 3d for pure over the top comedy and fantastically easy user created content), but... erm, hey, it's not out yet!
But I can't make this choice for you, but can very easily say: You can play Halo 3 in an hour if you go to Wal-Mart right now. You can play FFXIII on your 25th birthday.
See Ya George.
"He did not die - He passed Away"
At least following a comedians own jokes makes his death easier.