Whoa, hold on there a minute!
Baldur's Gate 2 (which I haven't beat yet) is much more story-focused, so if you like the story you'd like the game. The characters interact with each other much more and have more personality than most of the ones in BG2. It's a pretty badass game, but it did take out my favorite aspect of BG1, which was the random exploring. You can't explore the world map like you could in BG1, which was sorta a downer for me, but the tighter story makes up for it. If you liked BG1 you'll like BG2.
However...
NWN is nowhere near the quality of the Baldur's Gate games. The (in my opinion) lucious, detailed 2D graphics of BG has been replaced by a bland and limited 3D engine. The story swings between really moving and intense to boring to completely retarded. The fighter class is worthless compared to nearly all the others, having no rediculous uber-attacks that kill big creatures in one hit like nearly all the other classes. Your partner will wander into danger and get cut up good during nearly every battle, forcing you to revive them every time... and I could go on.
Basically the compromises Bioware made to NWN to make it a big online game and easily modified hurt the single-player game, and the single player was not up to the standards of BG. If you want to play multi, I would imagine it's sweet, but I wouldn't know considering my school blocks NWN's multiplayer ports.
And to anyone who's played it and beat it, imagine my frustration: I got all the way to the area right before the final battle as a level 14(!) fighter. Like I had a snowball's chance in hell of winning that battle. 