I'll chime in on this (very belatedly). NWN literally changed my life and career -- it got me interested in coding which I had never done prior to NWN. It's astounding how flexible, powerful, and easy to use the toolset is and so much of the content created for the game surpasses titles made by AAA developers. I prefer many NWN campaigns to Dragon Age, for example. Also prefer said campaigns to Mass Effect 1/3 (Mass Effect 2 was utterly amazing, though, and my favorite single player game of all time).
Releasing a toolset like NWN's is nearly unheard of -- the idea that you can create campaigns and even online worlds without having to build an engine and art assets from scratch is amazing. Some other toolsets have nicer graphics or improved mechanics -- but then they suffer in other ways. SC2, for example, cannot host a continuous game online -- nor can you save and resume an online multiplayer game to my knowledge.
NWN is pretty unique and amazing in that regard.