Hack and slash games need not be like Devil May Cry, that's just one hack and slash game.
I disagree. This was a genre made by devil may cry. Musou games are their own thing.
That lack of categorization is what leads us to the ridiculous action-adventure genre wich can encompass virtually anything.
Wolfenstein 3D made the FPS genre. Far Cry plays nothing like it, yet its an FPS game.
A game can start a genre, but other games can expand the genre into new territory, they need not be based on where things started, and Dynasty Warriors plays like what a hack and slash game would play.