To me, RPGs have always been defined more by gameplay conventions than the actual "playing a role," thing that some people (in and out of this thread) get hung up on. Yes, character can be an element to it, and in most classical cases is, but let's examine a couple of things.
1. Old school console RPGs, specifically JRPGs, were quite limited spatially by what was possible. Take Final Fantasy, the original. I believe that this was basically the closest a FF got to riffing off of Dungeons and Dragons wholesale, near to the point of plagiarism. To sort of "shorthand," the character creation aspect, they provided you with a set of four characters who had no background, no names, and no classes. This, essentially, let you create a headcanon of four characters who could be basically anything within the confines of the game's world. They could all be orphans from different corners of the world, they could all be edgelords pulled in from another dimension who hate Chaos, or, my personal favorite, they could all be male strippers from Pravoka.
2. As time went on, the medium dictated that having silent protagonists and audience stand ins was antiquated, and a more narratively flowing, character driven tale was expected, and the status quo. Saying that a game doesn't qualify as an RPG because it's lacking elements that it's real world, physical counterpart doesn't have is being unnecessarily rigid. With things like sports games, I could see the point. You aren't physically throwing that ball and running through the field. You don't have to maintain a level of fitness and exercise. These things fundamentally change the game. Madden games are essentially RTS games for people who would beat you up in high school if you said you liked RTS games. But with traditional RPGs, certain things have to change for the genre to remain afloat in another medium.
3. I think what another user said here (can't remember your name and I'm lazy, sorry) made a lot of sense. An RPG in a contemporary sense is a game that is built from the ground up and dictated by statistics. Random number generators. Equipment. Accessories. Weapons. Armor. Dramatic boosts according to levels. Weaknesses and resistances. Buffs and debuffs. Other games have little pinches of RPG flavoring, other games have far more. I think it's politically correct to say Assassin's Creed is an RPG now. Now, were we to go back to say, Unity or Syndicate, I'd say it was a stealth game with RPG elements. I haven't played Horizon yet, so I can't dictate what my opinions are about that just yet, but we'll see.
