1. It's meant for kids!
2. Collect all the useless trinkets, beat some side quest that's harder than the rest of the game combined, beat it in one life, or some other ridiculous arbitrary optional crap!
3. Play on a higher difficulty setting!
FO recently debunked #1, and quite nicely I might add. #2 has been debunked in bits and pieces in FO's Lufia 2 review, the random thoughts on Aria of Sorrow Crawl had on his main page, and my LEGO Star Wars snippet of my overrated games article. Let's talk about #3.
With a few exceptions, say Goldeneye adding new objectives on higher difficulty settings, or Power Blade adding recoil, all upping the difficulty does is increase the enemies' HP and the amount of damage they do. For example, if I played through Normal on God of War and thought it was easy, somebody might say "play on Spartan". Now, I did play on Spartan my first go through, and it was mind-numbingly tedious.
Also, if you've already played through a game, you've already learned all, or at least many of the tricks, which might be why I thought MDK2: Armageddon on Hard was easier than on the Dreamcast. A higher difficulty setting probably isn't going to offer anything new, especially if all it does is make enemies take longer to kill.
