Neverwinter Nights all the way, I've got a thread with a screenshot a few threads below this. Morrowind was OK, but it had a clumsy interface and was too open ended for my tastes. (Very little cohesive storyline driving me on.) I also didn't think that Morrowind had decent graphics at all. It had nice landscape, and the water effect was excellent, but all the textures were extremely washed out, and low res in feel. The characters were also way too blocky looking.
Neverwinter Nights however has an excellent storyline which you can play through in any manner you wish. You can play a virtuous Paladin saving everyone, or you can murder people and take their money to buy better weapons. 😈
NWN also has an excellent interface, probably one of the best I've ever seen, and it just reeks of quality. The graphics are also top notch, and Morrowind shouldn't be compared to it at all let alone think that the graphics are better. The grass effect is worth the price of admission alone (As you walk, the long grass pushes aside instead of your character clipping right through it as in other games.)
Add in perfect music, excellent sound effects, spell effects up there with the best games (except Final Fantasy's Summons, nobody has beat those yet...)
I gave up morrowind out of boredom and frustration (terrible combat controls), and I'm about halfway through NWN right now, and I can gaurantee that I'll be finishing this one, as it's the best game I've played in years.