I think part of the problem is that many elements or features come together to create an RPG, and not all of them are necessary. Is the game still an RPG when you remove or replace one or more of those elements and features? If not, then what kind of game is it? Perhaps some games that resemble RPGs are considered RPGs simply because they don't fit any other genre label, which leads into my second point: The other part of the problem is that "role-playing game" has been an ambiguous term from the moment it was coined.
Everyone has their pet elements that they enjoy the most, and if one or more of those elements are missing in RPG X, they're inclined to think it's decline... or not an RPG at all.
That is a good start.
In my opinion, the answer, whatever it is, will unfold once people stop quantifying RPGs with binary lists, and instead begin to qualify them with tags.
I think that the community around Visual Novels (insert the mandatory rolleyes.gif here) had a good take on how to achieve this for their games :
have a look.
Of course, there should be a special <dumbfuck> tag for DA2, but that goes without saying.
It's impossible to determine the elements that make up a RPG because you can have several answers that contradict each other, all of them valid.
Agreed.
That is probably why we should have a very loose definition of it, since there is a good chance that we will never manage anything more concise. Still, this is better than nothing, and probably nothing more than people will ever need if they wish to talk about RPGs in the future.
Over time, the list of valid tags could be discussed, moderated and refined, till we get something (a cloud of tags) consistent and mostly undisputed on the Kodex.
At that point, making lists would imho actually make sense, since we wouldn't be mostly comparing apples to oranges : list of party-based, turn-based dungeon crawlers, list of real-time, sandbox-style with strategic elements, etc.