Never Winter Nights is the closest your going to get to an actual D&D experiance. The single player story is very good, but the multiplayer is very much like what you would play in real life. A person (DM) constructs a world based on a story line he either made or or pervioulsy existed. People join in on the game and you play out the story line. I never got into the multiplayer much of NWN but seems like it could be allot of fun.
Everquest, in my opinion is the crappiest game I've ever seen. I have no idea how it holds such a large player base. The basic premise behing EQ is that it is a Massive Multiplayer Online Role Playing Game (MMORPG). You create a character, run around, and kill things. That's it, sure there a few large mobs that have better items and you can gain levels and what not, but there is no real story line to the game. Bashing on NPC's (Non Player Characters) for hours on end day after day, just to get an item has never been my idea of fun. UO (Ultima Online) back in 2000 was one of the best MMORPG's out on the Market because of the diversity and the PvP (Player vs Player).
But really it all depends on what your looking for, if your looking for more of an actualy D&D style game NWN is the way to go. MMORPG's are not very story driven, the game is what you make of it, the people you encouter and the things that you do.