Kratos is the one I would less want coming after me, but that's primarily because being illed by him would be one of the more horrible deaths you can experience.
As for who would kick whose ass? Probably Ryu. Hope won't avail Kratos against Ryu, and when it's down to their base magic vs. magic and skill vs. skill, Ryu borders on unstoppable.
Yeah. Ryu would take this every day of the week.
Having an opinion that doesn't agree with mine means I am sexy and you pale in comparison.
I really don't think comparing magic and skill across 2 completely different style slashers makes sense.
And I thought I'd discuss Ninja Gaiden a bit. My experience with NG was limited to the NGS demo, which I hated because of "meh"ish jumping mechanics and the horrible camera.
I "might" get a game as a gift, and I'm slasher hungry at the moment and debating whether to ask for Dante's Inferno, Bayonetta OR NGS2. (keyword here is might)
So, is it harder than God of War on very hard ? (I'm a completionist, and I like to platinum all my games) and how long is it compared to the other 2 ?
Comparing skills across two different games is the only way this can work. Ryu Hayabusa's greater speed, magic, and weapon skills would eat Kratos alive.
If you don't have any experience with Ninja Gaiden, you don't have a lot of room in this debate...
Listen, Bayonetta and Ninja Gaiden are really different from God of War and Dante's Inferno. Bayo and NG are much more technical and in some ways more frenetic than GoW and DI. They don't play much alike. If you want a game that plays like God of War, get Dante's Inferno.
Ninja Gaiden and Ninja Gaiden II (or Sigma and Sigma II, I guess, though the originals were superior in both cases by all accounts) are about as long as God of War or Bayonetta, depending on your skill. Ninja Gaiden games are also easily the hardest in that list, and Master Ninja makes even Chaos Mode look like a walk in the park. But, again, that only holds for the Xbox versions of those games, I can't speak for the PS3 versions.
To remain on topic: Ryu Hayabusa would kick Kratos's ass.