I've come to believe that any successful MMO is very much a matter of needing to be in the right place in the right time. I guess it's the lightning in the bottle effect.

I also think that any MMO that doesn't already have a lot of nostalgia to lean upon is going to struggle immensely. I doubt it's a coincidence that the most prominent MMO's I can think of at the moment are FFXIV, GW2, ESO and WoW.

FFXIV naturally has a lot of Final Fantasy titles to send a nod towards. Guild Wars 2 is the sequel to Guild Wars, Elder Scrolls Online references the single player games and shows regions we never got to explore within those same titles. As for WoW...its golden years are very much based around the Warcraft games.

There's players who have never touched the games that inspired those MMO's, of course, but I think the number who stick around due to wanting to see references is not an insignificant amount.

I'd love to see more healthy competition where the MMO market is concerned. Yet any upcoming MMO is going to struggle, I fear, unless it truly brings something ground breaking to the table and doesn't skimp on every aspect of the game. So it needs a good story, an immersive game world, an excellent soundtrack, decent character customisation and above all else it needs to not have any major flaws during the launch period.