The base campaign is kind of awful. It really just existed to demonstrate what you could do with the tool set. The expansions, Shadows of Undrentide and Hordes of the Underdark, are much better written with more interesting characters. None of the three campaigns hold up to modern game writing standards and all are pretty heavy on dungeon crawling. The deciding factor is probably going to be how much you like the D&D 3.0 rule set.

Obsidian's sequel is based on D&D 3.5 and the core campaign has writing roughly on par with the first game's expansions, with the quirk that it's Obsidian doing high fantasy straight rather than their usual deconstructions. NWN2's Mask of the Betrayer expansion is easily the best written thing out of either NWN game and is genuinely pretty great. NWN2 has some pretty terrible optimization, though, and runs rough on even high end modern systems.