Mario bores me...

[Zero Kirby]

I agree completely. Mario games may have been hard once upon a time, but then we got good at video games so everyone's nostalgia about challenging Mario games is likely to not stand up nowadays. The Lost Levels doesn't really count, because it's literally a stagnant game and the "challenge" is just really bad level design. When I was a kid I was never able to beat Super Mario World past Vanilla Caverns (or whatever it was called).

Another thing may just be that being able to save your game lets you start from World 2468273-4872 whenever you want, so that definitely cuts the "challenge" since you don't have to get through all those first levels again, and you have more time to practice the later ones whenever you want.

Mario games need to be accessible to everyone - the difficulty of them, I'd say, hasn't changed much, just the skill of the players. If I was five years old again New Super Mario Bros. Wii would probably be a challenging game. That's not to say that they shouldn't be challenging in later stages of the game, which they are (excepting the portable New Super Mario Bros. games, which seem to let you walk through them in your sleep). The early levels will always be easy and the later levels will only get easier the more Mario games you play.