I'm with you on that. World 7 in Mario 3 was definitely harder for me than World 8. Especially the last two levels before the castle (at least I think those are the ones I'm thinking of). I know I've beaten them at least a few times but I know a lot of times I resorted to using a warp whistle at that point.

I think I have an emulator that keeps the games playable. I'll have to check later. I really want to play now.