go find planescape: torment. >>>>>>>> BG2
For whatever reason, I don't really think of Torment as an RPG. It's all about the story and characters in it - actual tactics and combat are rather easy. Overall package, BG2 is the winner, although Torment has the better overall plot, story structure, and (some) better characters.
BG1 is also good. It starts out a bit tougher than the sequel does, though in the end I think BG2 is the harder game. Unfortunately, after playing BG2, it's very difficult to go back to the first game's iteration of the engine. There's a mod somewhere that lets you play BG2 using the BG1 engine, but last I checked it was pretty buggy.