Final Fantasy VII pwns everything hands down. Best story, some of the characters, including best villain =P (everyone loves Sephiroth and his sheathless Masamune, hell he's even got an ESF model, along with Cloud). If you play FFVII, you can't go wrong.
Edit: and to everyone who chose Diablo II, not that I hate it completely, as I used to play it a ton, but I fail to see why a game that has resorting to endless hacking and the "infamous hell cow run nonstop" along with nonstop twinking and remaking your characters over and over for no other reason than to rush them to said hell cow run and lvl them 70 times in 4 hours so they can wear their hacked, "l337" equipment that you bought with 700 SoJs (none of which are real SoJs mind you) and later go "duel" (or in the barbarian's case, "Whirl till you hurl" your opponent) so you can kill the stupid people who may or may not have the EXACT SAME equipment as you which would have also been bought by 700 SoJs or whatever. After killing them, you insist and saying they suxx0r and that they are n00blar and you are "gosu", especially when half the people don't even know what gosu means and only say it because they are 11 year olds and think its cool to copy what people say.
I mean come on, the game is pretty fun for awhile, but do you really need to kill thousands of cows an hour (or in most people's case, they just leech exp off the other players in the game because they are lvl 5 trying to lvl in a lvl 75+ environment) just so you can wear your new "Cruel Ith Zodded 160/60 collosus blade that r0xx0rz j00r b0xx0rz n00blarz!". I can kinda understand if you like the game, but it just kinda makes me wonder why it is your FAVORITE, But that's just me and no1 cares about my opinion.
*Goddamn that was a LONGASS edit*