I find Baldur's Gate better than its sequel, due to the low-level campaign and limited possibilities for exploration. I still remember the large amount of absurd encounters one could have in random places (for example, the child looking for his dog who turns out to be a shapeshifting demon, etc).
The boss fight against Sarevok is also much more compelling than Slayer-Irenicus, and almost impossible to win without cheesing. Not to mention Durlag Tower - best dungeon of all time.
I also think Irenicus is one of the most overrated videogame antagonists, pretty much the Sephiroth of western RPGs. A mage who tried to reach above his station, predictably failed and then went on a mad quest for revenge against the world. Yey.