Ultimately there are two big problems here. Genre is not binary. Why do you think the term "rpg elements" got penned? A game does not have to fall into one exclusive bin. The second problem is simply that currently we simply don't have the technology to replicate the experience of sitting down at a table with some friends and playing a tabletop role-playing game.
So when it comes to video games though, for me at least, it all comes down to your sense of identity in the world and to the character. I may play the role of Gordan Freeman in Half-Life, but I am not role-playing as I would be in say my character in Dragon Age: Origins.
So while many games, JRPGs for instance, might be branded as RPGs. I do not believe they are in the original sense of the term. They can however be defined as such in meaning that has cropped up as it relates to video games.