I'm not sure asking people about what the best RPG in their opinion is and only providing 3 voting choices is the right thing to do but anyway...
I'd say Oblivion is likely the best RPG i've played so far, either that or Sacred 1 or 2. What would really kick ass IMO for an RPG would be Morrowind with Oblivion's combat system (and better graphics of course). Hoping Skyrim is something to that flavour, but i'd expect it's just going to be a nicer looking Oblivion with a different world... (like New Vegas is to Fallout 3 minus the nicer graphics part)