I bought and played BG2 a year or two ago and loved it (though I still haven't finished even my first play-through, I got stuck during the long epic endfight of the expansion and haven't bothered returning to it), but when I then tried to play BG1, it was just frustrating because it wasn't as good as its sequel, or at least missed some of its functionality. You might have the same issue with BG2 itself for all I know. Still, it has a solid story, some fun character interaction and a lot of clever and varied quests to do, at the time of its release it certainly was a stupendous game.

Of course, I've played very few other RPGs to compare with, except Neverwinter Nights (of which the original campaign isn't nearly as good as BG2, but it has the immense advantage of having tons of player-made campaigns, some of which are incredible).