Me and MMORPGs have had a bad relationship. I think a lot of it boils down to me just not picking the right one(s).
For a while I had the original Everquest and a few expansions for it. Unfortunately I didn't have all the expansions and I joined after the release of Everquest II so finding people around my level (especially people who stayed around my level, since I played very casually) was difficult and after my three months of subscription, I left.
Other than that, I tried free games like Anarchy Online. I had a brief bout with Gunz: the Duel (I realize its not a traditional MMORPG). Overall I was just finding that I didn't want to make the time investment and I found the worlds overwhelming and boring. Other than that I found I was both incompetent at the social aspect of them, and was as a result mostly playing for myself, which really didn't work.
I tried World of Warcraft at a buddy of mine's house. I really didn't enjoy it. I wanted to give Final Fantasy XI a try, but I never got around to it. I think I could have gotten into that universe a little more easily.
Who knows, maybe I'll give Dungeons & Dragons: Online a try now that it has no subscription fees...
As for other genres? I don't know. I really like a good deal of JRPGs, but I've never really played ones that weren't critically acclaimed. The only examples of ones I didn't like were ones that I played for a few hours each and dropped because of that very reason. I didn't like the Lufia series, nor the Shining Force series. I was bored by Final Fantasy VIII and the Dragon Warrior/Dragon Quest series has never been interesting to me, even if I loved playing Dragon Warrior: Monsters for my Gameboy.
I couldn't ever get into sports games with the exception of Tony Hawks Pro Skater 2 if that counts. The reason being (in most cases) that I've never like playing games I could just go out and play in real life, with a few buddies and have way more fun. I also didn't like racing games. I've just always found those two genres inaccessible to me.
Overall though, I think there are so many genres for that reason: because we all have different tastes. Just because you've branded yourself a "gamer" doesn't mean you have to like every game, or every genre or every game of a genre. It just mean you like playing the games you like playing, which are, in general, many.