I'm gong to stretch the definition of MMO, so bear with me:
1) Diablo II (about 6 months)
2) WoW (off and on since release)
3) Monster Hunter Tri (about 6 months)
4) DC Universe Online (about 2 months)
5) Guild Wars (less than a month)
6) SWTOR (about one month)
I've fallen back to WoW periodically over the past six years, but I really feel it's crashing with the Cataclysm expansion. I mean, I downed Deathwing for the first time the other day, more out of boredom than anything, and had no feeling about the experience whatsoever. No jubilation. No satisfaction. I don't even think I smiled. The whole expansion just seems...lifeless.
Out of all the games I listed above, my fav is probably Monster Hunter Tri, so I'm excited that TERA has a comparable combat system (i.e. no tab targeting).
My least favorite was easily Guild Wars. *shivers* The combat in that game was just so, so bad.
I've checked out most major MMO's since they stopped being MUDs.
Hoping Tera will have staying power as I don't really put GW2 in the same genre and MMORPG's seem to be falling off a cliff after this.
Failing this I guess trying out Planetside 2 or waiting for a time long into the future when Bethesda finally gets the rights to make Fallout Online.
MMO's i've gone through in various stages
City of Heroes/Villains
Guildwars (about a few days lol)
and now TERA.
"WoW players are carebears they ruin everything they are so immature WHAH WHAH WHAH!"
The majority of people who played WoW and would come to a game like this are people who started playing it very early on, when we were young, when it was supposedly fun, and before it became a fluffy cupcake of carebear entrails. Don't blame all of us who have played WoW for years, sticking with it more than likely due to friends and familiarity, for the few people who bandwagon onto a game like TERA and are disappointed that it isn't just like their beloved mushy WoW experience or whatever and cry for all your "WoWinization nerfs." Just because the game is now populated by 12 year olds who cry everytime you look at them wrong, doesn't mean everyone coming from the game is like that. 95% of the population represented or not, your generalization is not very useful in this case.