When I was able to get a hold of arcade/snes/nes games on emulators I replayed all of my hardest games. I beat all of my top twenty in a weekend.
How? Because all the emulators came with Quick Save & Quick Load. F5 and F6 are the major reasons why games are easy these days. It's a night and day difference. Playing some of the ultra-hard NES games became a walk in the park; really just repeat the last action until success. I even beat the arcade versions of Ghosts & Goblins, then Ghouls and Ghosts in about an hour for each.
I've been playing a ton of nethack lately and I really wish games like Skyrim and other open-world-games had a 'permadeath' difficulty setting. Sure, I can choose to play that way, but I like it incorporated into the game. I want a system where it difficulty is just a percentage of more guys & less ammo, rather difficulty should be a fundamental change to the game.