Icewind Dale is very little like Diablo 2, in all respects except its ability to be played for hours whilst forgetting the time. Though personally i think Baldur's Gate 2/Throne of Bhaal is Diablo 2's main competetor, as that was really one of the biggest last-generation rpg's with really addictive gameplay and storyline.
It's a whole new world if you're used to Diablo 2 though. D2 goes something like:
*kill, kill, kill, run, w00t itamz!, kill, kill, kill, kill, run, killl, run...*
Wheras BG2 is something like:
*walk over here, pause, detect traps, pause, disarm traps, collect items, walk through doorway, pause, see enemies, pause, tactically decide how to combat them, arrange party in battle formation, pause, cast carefully selected spell, pause, have fighters attack, pause...*
Gameplay's alot slower, but can still be as addictive if you enjoy a more story-oriented rpg. Hope this helps somewhat.
Edit: typo