I think a big problem with the name "MMORPG" is that it describes a goal, not a genre. If I wanted to make a FPS, and Valve Software wanted to make a FPS, they'll both be the same genre. However, "MMORPG" describes a goal: 'massive' (whether you are defining 'massive' to mean content, world size, subscribers). Since it's describing a goal, not a genre, that means a game that wasn't an MMORPG early in it's life, can become an MMO later in it's life, just by increased player count or world expansions. With the exception of World of Warcraft and Lineage 2, no game hit 1 million subscribers within it's first year of release (at least, as of 2008).
This is why ORPG is so much a better term than MMORPG. World of Warcraft is a commercially successful ORPG. Success is also relative. If I made a game, and had 1,000 subscribers, I'd consider it successful for me as an individual.
It's a Massively Multiplayer Online Role Playing Game. The massive refers to the number of players, not the amount of content.
They use massively multiplayer online role playing game because there are online role playing games that are not massive. NWN is a good example. I think it has a max of like 16 players per server.
A lot of people take it to also have the implication of a persistent world, though that isn't necessarily accurate by the acronym. There is definitely a difference in the number of people on an MMO and any other online game.
