For me, the connection is more with the people I play with than the MMO itself. Yes, CoH affords the ability to make endless character iterations possible, with only your imagination as a limitation (for the most part). But if it wasn't for the people that I met and played countless hours with over the course of years, I don't I would have stayed with CoH any longer that I did with EQ (3 months) or DDO (1 month) back in the day.
Currently I do play DDO with some friends and it seems like every day I play I come across stupid design decisions in the game, so often that I quit saying "That's so stupid." and say "That's so DDO." instead. But I play because I enjoy playing with my friends. Which reminds me that I need to spend more time in CoH with my friends here, RL has gotten me down and I've become unsociable.