Nothing has come close and nothing ever will. Mainly due to the fact that it wasn't just the game mechanics; but that all player types had no other option except to play UO. This, combined with the game mechanics, is what made UO a one-of-a-kind experiences. I feel blessed and honored to have had the opportunity to be a part of it. After so many years failing to find a UO replacement; I've accepted this conclusion as reality and as result, have stopped searching.
Star Wars Galaxies was another absolute gem at its prime. I never played it, but reading stories about the game makes me feel it's the one game apart from UO which truly came close to fulfilling the promise of a "virtual, persistent, shared world".
He has a book called Postmortems where he compiled essays (many found on his web page) about his early days writing MUDs and developing fantasy worlds, including UO and SWG.
DAoC had some of the better PvP mechanics of that generation of MMOs. I played DAoC for years, and eventually moved to WoW for a little while. WoW always felt too easy and never really gave me the same rush that DAoC did.
I still remember the day I gave a friend of mine my DAoC accounts. He later sold them when he quit, and gave me some cash back :)
