Can't say that I really play (nor have I found) any good multiplayer RP games except for Disco. I do quite a bit of SP RP in Skyrim and Morrowind, but that's not really the same as Discovery's RP nor as fun. I'd bet that there are some alright RP communities/forums out there based around the TES series (and other RP-friendly games) to make them, uh, multisingleplayer for lack of a better word, but I haven't really been looking all that much for them; Disco already fills that niche rather well for me.