Gearheads of War

I was wondering about the Gears story and looked up in different forums to get the timeline right. I hope that everybody who reads this, is through the Gears2 campaign, if not - you have to decide for yourself if you want to read further.

This is going to be a wall of text - enjoy :)

Currently I'm playing through the insane campaign and was wondering about the difficulty and what you think about it? To my mind the three difficulties are adequate. Insane is hard, but you can do it with a little practice. And the easiest grade can be mastered even by casual players. You can improve your skills by trying harder difficulties and that prepares you for MP action.

In that case I wondered about the hardest games I've ever played. I can remember Earthworm Jim on the SNES and Battletoads in Battlemaniacs (also SNES), which had the hardest difficulty I've ever seen in a video game. At that time I wasn't able to beat stage 3 and I'm not sure whether I could do it now. What where the hardest games that you have ever player?