Did you guys ever consider that maybe you're getting better, and the level of difficulty hasn't changed as much as you think?
I remember when Super Mario Bros. 3 first came out, I could not get past the third Land (the water one) no matter what I did, I could not get through that spot without a whistle. I picked up the game and started playing it again a few months ago, and tore through the third World like it was nothing. As I did with the fourth, fifth, and the first half of the sixth and beggining of the seventh (that's when it starts to get sticky).
Maybe the games aren't getting easier. Maybe you're just getting better. . .