Collins does get hailed as the first detective story writer - or the first crime mystery or... But surely he postdates Poe.

I suspect many people are making a quality judgement when they say something is or isn't (transcends?) genre. For me the point is utility - how useful is it to read Hamlet in terms of ghosts rather than, say, revenge?

I could envisage us claiming something as sf (PD James's Children of Men? Works by Atwood?) and then saying, it isn't very good.

Note also how geniuses have artistic unity but hacks are formulaic.