I have to disagree. I think making a hard game that is still fun is very challenging. But when you accomplish it, it's an even better platformer than the not-so-hard one. Take Donkey Kong Country Returns (Wii) and Rayman Origins (Wii/360/PS3). Both are very hard, especially DKCR. But they are very hard in fair, legitimate and satisfying ways. Beating the later levels in DKCR takes a bit of dedication, but is oh so satisfying when you get in the zone and find that beautiful path through the level.
Also see Super Meat Boy. It's basically a hard as nails platformer where you can and will die hundreds if not thousands of times trying to beat it. It's another great example of very hard (it's way harder than both RO and DKCR), but still fair, fluid, and "zen-like".
I don't think any automatically generated levels could ever reach the level of flow that the games I mentioned have, though.
Hard and fun are completely different things, I agree. I spent about 3 months on the basic algorithm, making sure the levels generated were feasible and interesting. The remaining 3 years have been spent making the game fun. The real trick is tailoring the difficulty to suit the level of the player. When you nail this correctly it leads to a very satisfying experience (and the algorithm does have a sense of 'flow' when it designs level, although I can understand that's hard to believe without playing the game)
Also see Super Meat Boy. It's basically a hard as nails platformer where you can and will die hundreds if not thousands of times trying to beat it. It's another great example of very hard (it's way harder than both RO and DKCR), but still fair, fluid, and "zen-like".
I don't think any automatically generated levels could ever reach the level of flow that the games I mentioned have, though.