Minecraft is the only thing I can think of.
I enjoy the challenge of games, and every game I have played on easy difficulty, just gets boring after a while. Halo on easy? Sure you can run around and beat the whole campaign by meleeing everything, but that gets boring after the third or fourth level. Mortal Kombat? Sure its fun to completely dominate the enemy, but when you play multiplayer next, you are absolute garbage because you have to get used to people fighting back again.
For me, I enjoy games the most when it is just a LITTLE bit easier than what I am used to. Like playing Halo on Heroic or SC2 on Hard. Then you still have to pay attention and know what you're doing, but you can't go completely crazy. You can't SCV rush or melee everything to death (although it is fun to try, lol). I think games are their funnest when you find the optimum difficulty where you have to REALLY try and be good at it, and then dial it back a notch. Then your hardcore tryhard mode is absolutely dominating everything around you.
Kind of like when you get thrown into a game lobby of scrubs and you've played about 10 days on multiplayer alone, lol.