Tetris. Best RPG evaar!
You can't beat the original Deus Ex. It has a very deep and epic storyline, dynamic problem solving, amazing soundtrack... What's not to like?
FF is good in is own FF way. Fallout and Elder Scrolls are also good in their own way, but none of these games have one levels worth of the dynamic problem solving that Deus Ex does. In Deus Ex, I can go through the entire game without having to make any unnecessary kills and I would still be well rewarded. I can stealth through with a baton, taser, crossbow with tranqs, and silenced sniper rifle (for tight spots).
Compare that to the rest of the grindfests that use the equation: (1) kill, (2) quest, (3) ???, (4) profit.
I heard Human Revolution was a bit of a let down compared to the original. I haven't played it yet though, so take this point with a grain of salt.