I'm not very good at Gears of War or League of Legends, but I still play them.
I'm crap at most football/rugby/american-football games.
I used to be crap at racing games and WoW, but I'm good at those two now.
I'm okay at puzzle games and therefore thoroughly enjoy them.
I'm not very good at Skyrim despite completing Oblivion on PC on Hard, Fallout 3 on 360 on Expert & Fallout: NV on 360 on hardcore. I've only just managed to play with the difficulty on normal - I'm ashamed of this as I know the lore & expanded universe like the back of my hand. :'(
Inversely, I'm bored with CoD and getting bored of Halo as I would say I'm in the "9th tier of skill"[footnote]2 under MLG, as MLG isn't a skill but a pathetic lifestyle - assuming there are 10 tiers of skill where tier 5 is a 1.25 k/d and decent objective capability (or equivalent), tier 1 is someone's first few games and tier 10 is god-like with the odd death; and are too moral/lively/humane to become MLG.[/footnote] in both. While CoD never changes enough to make it interesting, the games themselves require minimal usage of the brain therefore fail to become a challenging/fun experience for me (aside for the many many bugs and balance holes). Halo, on the other hand, keeps you thinking throughout almost any online match, unless you're playing against a really shit team. But alas; pointing at things and shooting can only be fun for so long...