The issue is game saves. Super Mario Bros. took me about a year to beat, partially because my skills weren't as high as they are today, but mostly because I had to replay the same levels over and over again. If you could save at the end of every level, though, I probably would have beaten the game in a month or so.
I don't think we should get rid of game saves, of course, but they've made it so that challenge-based games don't work as well as they used to. Length is now of more importance.
Ummm...what's my point?? I guess, to make an Epic game nowdays, you have to find a way to make it last for a long time in spite of game saves. The result has been that a lot of epic games have become bloated from MIBS (More is Better Syndrome). I've played so many amazing 10-15 hour games this generation and so many merely good 40 hour games that suffered from collecting, backtracking and unecessary extras.