What is an MMO?

So we had a bit of a debate in work when someone tweeted this list of games:

Top grossing MMOs

1. LOL
2. Crossfire
3. Dungeon Fighter
4. WOW
5. WOTanks
6. Maplestory
7. Lineage
8. CS Online
9. DOTA2
10. Heartstone

While these definitely all have large user bases and are multiplayer games, do they fall under the "MMO" title?

If someone told me to sit down and play their MMO I have a pretty good idea formed in my head as to what an MMO is, something like Final Fantasty 11/14, World of Warcraft, EVE Online etc.

I wouldn't consider League of Legends to be an MMO and I certainly wouldn't include Hearthstone on that list.

What are your thoughts?

I don't think League of Legends belongs on that list at all. Even if you take "Massively Multiplayer Online" at face value, League of Legends is not massively multiplayer. It's 5v5. If that's an MMO then every single multiplayer game is also an MMO. Dota 2 doesn't belong there. Hearthstone doesn't belong there. That's generally a very poopy list.

That said, I think "MMO" was a term coined to show off the power of early MMORPGs by saying it's "one world" with hundreds/thousands of players. I think it's dumb to try and argue what is and isn't an MMO when we can just say something is either online or not. It's a category that probably doesn't need to exist honestly.

In my mind, an MMO must have a large (thousands, easily) amount of people on one server, able to see each other at any time if they all appear in the same place. The whole point of the "massively multiplayer" part is that you can get huge groups together and crash servers from how intense it is for the game. I feel that many modern "MMO-esque games" are getting away from this, making servers smaller and instancing the shit out of things (I'm looking at you FFXIV) mostly to cope with the need to have a wide potential userbase for a game and not make it require a beastly PC to run without frame drops.