Quote Originally Posted by Yamaneko
Super R-Type. Yep. I've never seen anyone beat this without cheats or without using a save/load state combo, which I did.
I beat it on the actual cartridge ;O

I actually thought Einhander was harder than Super R Type... But they're both incredibly difficult. Anyway I don't really know how to answer these questions because there was all these awful NES games that were nearly impossible because they were terribly programmed but if I had to answer the toughest game that was still a great game I would probably say Vagrant Story. The first time you play it you'll undoubtedly be doing 1 damage per hit to bosses at some point. Even when you know exactly what to do it still manages to be pretty damn hard.