Truly immersive mmo's

Let's face the truth, you will never find something similiar to Ultima Online.

Everquest, the original, they even have housing now

EVE online? Never played myself but for what I've been told it's more of a lifestyle than a game.

runescape is the only I've played that I can suggest. but the last time I played it was 4-5 years ago

World of tanks. A lot of roleplayers there. Mine steel and upgrade your little lvl 1 tank with additional armor. Get special sets and pick up a secondary profession. There aren't many, sadly most people are quite noobs and simply pick the easiest class that being a simple warrior and tanking for the group. Some go for the ranger / scout class. Wot devs haven't quite nailed the wizard class as the only spell currently is a long range fireball. Still it's quite fun doing, doesn't matter if you are collecting bear pelts or doing a dungeon raid in Berlin and fighting RoboHitler, it's always fun and immersing.

Persona Series (not MMO)

I would try Morrowind or maybe Oblivion. Not online but I'm not aware of any game more immersive.