Ponico made an interesting comment recently: "Before World of Warcraft incredible subscriptions, 300K customer was pretty good. I still think that when an MMO gets around 300K+ users, it's still a fairly decent success."

Which brings me to wonder- in terms based just on active subscribers, "What is a success?" Comparing every game to World  of Warcraft is not only unfair, but redundant. It is the same to me as using Hitler in a debate about something other than genocide or Facism.  MMO's were successful before the Blizzard Behemoth and they will be successful after the game has gone.  How many subs does it take to properly populate servers and stimulate proper pvp/rvr balance, auctionhouse economy, etc? We need to stop using WoW as a measure of success if we, as a community, want to encourage more innovation within our chosen hobby.

The number of subscribers that puts the game in a place where it is making money for the company. For some companies that's 250K, for others, like Icarus with fallen Earth, that's 50K.

Course, the web gurus will want to try toss numbers around like they know it all. But it comes down to the dollars and cents. As soon as subscriptions income > game maintenance costs and steady profit is earned, success.

A successful MMORPG, from a player perspective, is a game that has a full server.  That's it, that's all.

It really depends on how much it cost to make that mmorpg and to keep it afloat.

Success in an MMO?

The game is still running.

Failure in an MMO?

Game doesnt make it past year 1.

Success based on subscription numbers?

All depends upon the company. Some companies can be a success with 20k-50k concurrent subs, while others may aim for a higher number. Take EVE and Fallen Earth for example. They only host one world (the game server you play on - not the multiple servers it is made up of) and have all the players there. This cuts dwn on the overall cost of running the game (imagine having that same world replicated 20 times... thats 20 times the hardware required, 20 times the support personel needed, etc).

Success = Positive subscription change over time.

Having 1 million subs at release, then 300k 6 months later isn't success.  Starting with 10k and moving up to 400k over years is. EVE and WoW are successes, games that release and die off within a year or  two (lots of these: WAR, aoc, potbs) are not successes to me.