Diablo 2 sucked for narrative as Words of Wisdom said. The original Diablo had much more impact and also the story worked because it was very simple, the game relied mostly on it's unique gameplay.
As for Zen's unkind words to BG2. Yes the path finding sucked (what's new, find your own path). The story of BG2 was largely unrelated to the original. The first dungeon is long but nowhere near hard (if you play the rest of the game you'll discover hard), also there is a difficulty slider if it was affecting your enjoyment. Lastly, WRPG gamers are constantly begging for expansivenessn (as is evident by the Ultima series, the Elder Scrolls series, and many many others). BG2 did exactly what people wanted. Yes it was easy to get side-tracked by side-quests (imagine that) but they were 100% filled with fun.
I agree with you Zen I can not play BG2 or Planescape: Torment again. Not because they are bad or lack play value, but because I remember everything too well because I played the hell out of them and exhausted most of what they had to give me. Maybe in 10-20 years when my memory starts to go (like it hasn't already, ha) I can play them again.
Kotor did have very good narrative but the gameplay was lacking quite a bit. The light/dark system worked well in that it could really affect the story of the game.
I don't know if MMOs or MOs count in this. I think they should be classified differently, and I think Diablo 2 online should be lumped with them. 
Neverwinter Nights was a step in the wrong direction and possibly one of Biowares worst outings (though not a horrible game). I enjoyed Icewind Dale 2 more than NwN. NwN 2 rectified a lot the problems of NwN but you can't credit that to Bioware.
