So for what this is worth I have just taken a subscription to Ultima Online. Which means in 2016 I am paying to play on the official servers, which is clearly a sure sign I am losing my mind.
The game now has two clients. It had two clients for a while, but the old Third Dawn client I remember from the last time I played was canned. There is now an enhanced client and the old classic one which are both the same in features and options. Except the enhanced client looks a lot better, retains the same graphic style (while the art assets are different), and doesn't crash half as much (Classic goes dead as soon as I alt tab, and doesn't support Widescreen in a game where you want widescreen because the interface is an absolute mess).
For some reason, the community seems to disagree with me and claim the old client is vastly superior for reasons I cannot really fathom. I guess if you played with an interface for 20 years, you really do not want it to change (I have noticed that at work with people complaining that apps in command line interface that have been used sinces the 80s are better than their modern counterpart). While most often the old shit is better than the new shit, the interface improvements of the new client alone make the transition better. It probably doesn't run on some dudes Cyrix 166+ though.
As for the game itself, well, it is great and terrible for various reasons.
It is terrible because the game has something like fifteen servers and most of these are perfectly empty. Why they are not merging servers is something I cannot for the life of me explain. Finding another player is a rare occurence, even on Atlantic which is supposed to be the most crowded one. The enormous game world clearly doesn't help for that matter, although it is still fun to explore.
Gameplay wise, let's just say that Ultima Online is a totally different beast than World of Warcraft which I have also been playing lately. UO definitely took some cues from its Blizzard competitor (or are they even in competition right now ?). There is a tutorial area filled with NPCs giving you stupid quests (train your skill up to 50 ! Kill ten rats!), and in the other towns there are other quests that feel more connected to the storyline but also seem completely pointless.
Still, though, the main appeal of the game remains : contrary to other games even MMOs, Ultima Online mostly remains an objective-less game. You are dropped in the game world and pretty much can do whatever you want without anyone telling you not to go there or to please complete this mission. The game is not level based, and instead still is skill based. Being a tamer is still an option. Being a lumberjack is still an option. Killing stuff in dungeons in search for mad loot is still an option.
But at no point ever this will result in a popup window, a cutscene, or a dialog, telling you you are on the right track. If you are lucky, the skill check worked, and it resulted in doing what you wanted to do and also a skill increase. And you can sell the result of your work to buy better equipment, or buy a house. And that is about it.
In those words, Ultima Online's closest competitor or game that is the most similar isn't another MMO. It's simply Minecraft, which seems to focus a lot of hate from the Ultima Online community for another reason I cannot seem to understand.
