I've started to hate the term "Hardest".

Give me two months in Unity, and I can make a game that's "harder" than every game on any one of these lists. It would also be unplayable trash, that would prompt hundreds of "How the fuck are you supposed to XXX" responses due to obscurity. Part of what makes those listed games enjoyable is having a decent difficulty curve, compelling progression of skill demonstration, and a good feeling of reward. They're getting difficulty right.