I think the NES generation has the hardest games ( except for thoose "hard for the sake of hard" games like I Wanna Be the Guy. ) I remember playing Battletoads as a kid. I never got past the second stage. I got pretty good at the first one, though. Also Turtles on NES is hard, haven't played it that much, but I never get far before all Turtles are dead.
It is very logical, the budget was smaller which means there was less money for design ( and also less knowledge about design ) and less focus on testing. And when developer tests their on game, they tend to know the physics very well. And since they know the physics of it so well, they tend to make the game alot harder.