RTSs: I'm not a fan of watching the game basically play itself. Simply 'commanding' the action makes me feel relatively uninvolved and unimmersed.
Most MMORPGs: Mainly, most of them feel like the same game, and you spend way too much time getting so little done at a time to build up to basically nothing. By the time you obtain something you want you have no real use for it, and you typically just end up doing it all again. There might one day be SOMETHING that earns my attention, but as it stands, most of them aren't worth my time, attention, or monthly investment. Try strapping outside of monotony and we'll talk.
Sports: Why the f**k would I do this?! Realistically, there's nothing I can do here that I can't do IRL.
Simulators: (see 'Sports')
Pretentious "Interactive Narratives" (sub-Indie): Do I really need to explain?!
Most Racers: I can make exceptions for games such Jak X and F-zero for having something distinguishable and enjoyable to add to the experience. Besides that, there's really nothing to it besides a wasted investment. If you're trying to make a "realistic" racer, you may as well call it 'Driving Simulator #37'; except Forza and Gran Turismo practically already beat you to it.
Sandbox: This goes back to Sports. It's basically just manual labor, only it takes place on another plain of existence. Simply put, they're f**king boring, without even so much as a goal in mind. Thanks, but no thanks. I can find better ways to waste my time.