I find that playing every single genre keeps me constantly interested in games. I love every genre; I may not like all the game types in all of them (for instance, I can't stand sim racers but love arcade racers) but I've found that with experimentation you WILL find something to like.
Sometimes I'm feeling like playing an rpg, another time I'm up for some arcade gameplay, sometimes I need some fps gaming, and other times I may feel like going through a story so I pick up an adventure game.
I find that variety adds to ones tastes, and the more variety you experience, the more you start to love games. Variety is key. If all you play are rpgs, or sports games, or whatever game genre, then yeah you're going to get bored. But if you go into games open minded, treat them all as if they're average (because a truly GREAT and classic game is rare) then you'll find yourself enjoying A LOT more games than before.
If you aren't enjoying games, perhaps you need to lower your expectations, go on a break from them, or quit games altogether depending on your situation.