Before the flame war starts (I realize it's inevitable on this one), let me clarify what I mean by "true roleplaying": the game engine and "rules" place have as few restrictions as possible;. While most of the MMOs we play are allegedly roleplaying games, most of them define your role. A great roleplaying game lets you create your own role for yourself and act it out, similar to a character at an improv theatre. "Roleplaying" in most RPGs is sorta like being in Hamlet; you can put your own spin on it, but you're forced to working within the director's vision. Rosencrantz and Guildenstern? Great roles stuck in Hamlet.
Games like WoW can be considered "roleplaying," sure. WoW lets you become that burly dwarf that does a mean Gimli impression by gruffly saying, 'Where's the brew, mate?". But you're constrained by game limitations and people's expectations. For instance, if you wanted to role-play a "big bad dwarf that's a coward and wants to hide behind the priest's robes" well, that'd get old after the first instance and most likely ensure you aren't invited again. Yes, I know there's people like Naked Troll guy , but let's be fair, he's an exception in a game that derides people for not having the optimal spec on raids.
Second Life, however, lets you create a persona and "act" it out without many limitations. If you want to do the warrior thing (including the cowardly lion bit), there's combat sims. If you want to role-play a cute skunk that just wants his or hers tummy rubbed, well there's a sim for that. I'm purposely staying away from the much-hyped steamier side of SL and focusing on PG-rated stuff, but there's most likely a sim for whatever you like.
RPG seems to be the label for games that let you adjust your stats. Neverwinter Nights is considered a roleplaying game, but working my way through the single-player campaign, the only real role I could perform was the one the game chose for me. I could adjust my character 's stats the way I wanted to and choose a race and class, but I was on rails for the campaign. Oblivion is a little closer since I could ignore the main quest if I wanted to and instead choose a life of crime. In my opinion, a good RPG is more like a sandbox than a game. Second Life fits that description more so than people give it credit for. I'll concede the argument that Second Life is more sandbox than game, but it's "games" like Second Life that might force us to redefine what a game is.
What about you? What do you consider a roleplaying game? Would you like to see MMOs allow you create a role that goes beyond "Me dwarf. Me smash?"