Mount & Blade, because it has great combat mechanics, and because its tailor-made to be modded, so there are brilliant mods for it. It's only single player atm, but multiplayer is coming soon, they tell us. Soon is, of course, relative.
And epic: I like RS. It's just more relaxed than most RPGs, and it's cheap. Also, it's about the only one where words are spelled properly, seeing as it's run by Brits.
Anyway, this will be the last I'll say on the matter, as I don't wish to pull this thread down into an RS flame war. RS isn't worth the Promethium.