Honestly, to me, the gameplay has very little to do with what makes an RPG an RPG. Going by pure gameplay, Mass Effect is a third person cover based shooter and Alpha Protocol is a stealth based action game. Yet both of those, to me, are RPGs. Why?
The dialogue and choice systems. To me, an RPG gives you choices. Should I help this guy, or kill him? In other genres, killing him would be an instant game over. However, in an RPG, both choosing to help him or kill him are viable choices. The only result is a ding to/rise of the moral meter if there is one and the death of your soul, you murdering bastard.
For example, take Mass Effect, Feros. Remember that part where you need to subdue the colonists? In a different genre, subduing them lethally would be a game over. However, in Mass Effect, you can use melee attacks and the Thorian Gas grenades to subdue them non-lethally, or just open fire, with no consequence other than a different story path and a rise in either Paragon, Renegade, or both, depending on how many you killed and how many you didn't. To me, that is what an RPG is.
