All of my friends still play WoW, but I currently play Rift. My anecdotal evidence is the opposite of yours. All this says is that we are never going to pinpoint a reason why we play what we do. A lot of it is obviously attachment over time. It could also be labeled addiction...idk.
I think Mists is the greatest the game has been since TBC, but I'm not currently playing it. I wanted a fresh start, new experiences, and Rift has that for me right now. Will it keep me past my 6 months sub? Depends on if the game still has the 'wow factor' (no pun intended) when that time comes.
This thread hasn't comlpetely devolved yet, but starting what amounts to a direct comparison thread was probably not a good idea. I'm surprised it didn't get locked immediately.