Guild Wars 2 sounds like a good fit for you if you want to try an MMO. It fits just about every criteria except the last two, which are very subjective. GW2 is a B2P game that gets pretty frequent and solid updates. Immersion is really up to a person, but the game world itself is very detailed and easy to get 'lost' in. While you aren't going to feel like you are your character, you will get caught up in the game.
Other than that it's stunning visually, has a large focus on exploration, and costs the same as a console game. It was just on sale, might still be, so check it out.