...I'm _still_ playing the NWN OC. ToEE is amazing, but as soon as somebody reminded me of NWN, I was totally back into it. Since you can use all the new stuff from SoU, the OC has a whole different character. At the moment, I'm on my way to becoming a Shadowdancer.
All told, I've been playing NWN off and on for a year now, and when Hordes comes out, I'll probably be playing it for a year more. Level 40? 6 new prestige classes? Two henchmen? Henchman romance? I want.
At this point, NWN does look somewhat dated, but even when it was out, I found the texturing to be rather amazing. For example, BioWare snuck in the BG logo on a book in a bookshelf. It's clearly discernible among the other books.
Geometrically, it errs on the side of simplicity because you spend most of the game zoomed out. The lighting is gorgeous, and I really dig the way the grass blows in the wind and moves as your character walks through it.
I'd be inclined to agree with most people that offer the BG series as the pinnacle of the genre... except that there are a couple of glaring flaws that I can't forget.
Here's the one thing that trumps most of the positive feelings I have for BG/BG2: it uses 2nd Edition D&D which, quite frankly, is ass. It was fine at the time, and I did enjoy it. However, now that 3E is out, I can't look back without shuddering; I'll take a 3rd Ed game over a 2nd Ed game any day of the week.
I also can't forget how much of a nightmare trying to make an ideal party was. In BG2, were they _trying_ to make it impossible to play a non-evil party? Viconia, Edwin, Corgan... they're all uber powerful with _extremely_ high stats in their class' prime requisites (respectively, Wis 18 (!), Int 19 (!!), and Con 20 (!!!)).
Most importantly, they're _not multiclassed_, unlike most if not all of the good or neutral spellcasters (Nalia, Aerie, Imoen, Jaheira). Multiclassing just cripples their progression so you're left hurting when you need the high level spell smackdown.
Don't get me wrong: I had a blast while playing them. But as a result of these problems, they had little or no replay value for me. That, combined with the above, means that I have a hard time regarding either as the paragon of RPGs as most people seem to.
Of course, NWN's got its flaws, too, even once you just accept that it's basically the arcade version of D&D (which is a valid approach, but different from the approach taken by ToEE or the BG games). I have two problems with NWN that dwarf any other I could mention:
 XP. There ain't enough of it. Kill an extremely challenging dragon, and get 500 XP. Kill a boss with little effort, and get the same. Even if you solo it and do damn near every side quest (which is what I do these days), it's often still not enough to get up to level 20. Very frustrating.
 Treasure. With a few exceptions, NWN doesn't handle it very well at all. There are way too many containers, and each container has way too little treasure. Boss treasure, for the most part, is unsatisfying. (The exceptions are those cases when they check what you have Weapon Focus in, for instance, and spawn a magic item of that type.)
Now if you wanna talk Planescape: Torment... that's a whole other issue.
THAT game's brilliance outshines the stars.