I have been referring to our games as MMOs for the last while. This is mostly in reaction to the fact that “role-playing” has come to mean “character advancement” in modern gaming parlance. If you character levels up, with success as much dependent on character stats as player skill (don’t argue details on this point unless you can solo Arthas at level 10), you have a “computer role-playing game.”
Explaining Dungeons and Dragons to a World of Warcraft player, I was struck that the C/MMORPG take on RPGs is actually a return to its roots. Dungeons and Dragons sprouted from Chainmail, and it was an extension of tactical war-gaming that had each player in control of one character rather than one army. Exploring a dungeon was the archetypal activity: here is a challenge to overcome, here are your resources, work with your team to kill the monsters and get the treasure. Your (functional) role to play was tank or healer, not (the acting role of) the adventurous son of a long line of elvish sages. Acting out a character is an emergent activity in what we came to know as RPGs.