I don't mind how hard a game is, as long as its fair.
Medal of Honour: Pacific Assault, on the hardest difficulty, with crosshairs off, healthmetres off, etc etc is impossible. I died at leat ten times in almost every gun fight. But it makes you careful, it means everything matters, and it means, oh how it means that you duck and run, dive into cover, and pick your shots. What I didn't like was that this "realistic" setting also made the enemies harder to kill than you were: that's not fair. If it's realistic, they should die as you do. They shouldn't get back up after SMG bursts to the face.
In contrast, I don't like the "general cam" view in Medieval 2:Total War, not (really) because the camera restriction makes it hard for you to see force disposition and things, but because it makes it almost impossible to give orders to anyone very far away, as you can't tell the difference between setting them up at the end of your line, or two miles away.. That I don't like, and so I never play with this setting on.
On the whole though, particularly in FPSs, I want them to be harder. I've never replayed Bioshock because it was FAR too easy. Ok, ok I could not respawn, but the load times compared to respawn times mean that this isnt a practical option..