You don't know what you've been missing!
Halo 4 seems like it won't follow the previous story line at all (covenant, flood), so Halo 4 might be a good idea.
@"Mitch" and @"Tyler", don't worry you can like more than just one game.
It is possible to like COD, BF3, and Halo! Just because you like one doesn't mean you HAVE to automatically hate the other. That is just silly and childish. lol