Eh, I would consider it an RPG due to the looting. grinding, farming, and skill trees. So far there have been 3 or so "RPS" games, and I don't consider that amount enough to call it a new genre. But I replaced it on my list with Viewtiful Joe, so it's all good.
They
are RPG's, specifically the Shooter subtype of RPG's...
RPG is a pretty large genre with many sub genres
Final Fantasy series is Turn Based RPG
Skyrim is Adventure RPG
Fable/Kingdoms of Amalur are Action RPG
Borderlands is this new FPS subgenre, that I THINK Dead Island also fits into even though it's more melee than shooting (but only due to ammo limitations)
Just like FPS has subgenres of
Military Tactical Action (BF/COD)
Military Sim (Arma)
SP Adventure (Bioshock, Rage)
Co-Op (Syndicate)
Classic (CS, Unreal, etc)
sometimes a game kinda fits into 2 subgenres as devs try to innovate how they can by blending different elements together in new ways....
If you were to fully classify it it would be a "First Person Shooter Action Role Playing Game"... the action denominator because as as far as RPG's go, it more closely resembles Diablo than more "pure" RPG's
Really... genre definitions are just to make it easy to convey broad concepts about a games categorization quickly and easily to each other