![Evil Smilie :evil:](./images/smilies/icon_twisted.gif)
I have played many hard games, but I think that the most difficult would have to be Capcom vs. SNK 2. Not the whole game, of course. Just the "All Survival" Mode. In this, you have to face all the characters in the game (40-50) one after another in 1-round matches. The AI gets better as you progress through the ranks, and your life does not replenish fully after each match. Speaking as someone who is quite good at Street Fighter, this is the hardest thing I have ever seen in an SF game. I have yet to beat it, but perhaps I will one day.
Second place goes to Gradius 3 or Contra 3 for the SNES. I actually beat these, even though they werevery difficult (as most scrolling shooters tend to be).
Now it's your turn: what is the hardest game you've every played and why?
Edit: There's a typo in the title...how do I fix that?