Moving Between MMOs

MMOs are by far, my favourite genre of game, however with the abundance of different ones out there, how do you choose just one (or two).

I have played various MMOs but have never been able to stick to one in particular. The pure choice itself can be overwhelming and because there are so many, each one fights for our attention and picks at your curiosity with a new mechanic, or interesting new take (although most just work off the same general idea anyway). I have played many MMOs, including the below and many more:

- WoW
- Rift
- Allods Online
- Darkfall
- Secret World
- Guild Wars 1 and 2
- LOTRO
- Star Trek Online
- SWTOR

No one has managed to grab my attention to the fullest, and it will only be a matter of time until I move on to the next big thing. I'm a sucker for a good, or sometimes appalling MMO. Is it just me or does anybody else dart around them?