Okay, a little background and a humorous anecdote before I get into my problem: I was talking to a friend of mine today about video games. At one point, I brought up Mass Effect. He immediately said he hated it because there's too much talking (which I can sort if understand, even if it is, like my other friend put it, like saying "I hate Halo because you have to run in it"). Eventually, this discussion panned out into RPGs as a whole. When I asked what RPGs he likes, he said, and I kid you not, Assassin's Creed and GTA IV. Obviously, he has confused sandbox games with RPGs. When I called him on this, he said "well, there's a lot of freedom and you can choose what you do. Isn't that what an RPG is?" He then asked, if not, what an RPG really is. Now, I know what an RPG is, but I can't find any way to word it. All I could think of on the spot was character customization. So, I need help; what are the components of an RPG, and how can I word this in a way to differentiate it from sandbox games? I know the answer, I just can't word it.
EDIT:Another thing. In that same conversation, he called GTA IV a First Person Shooter. Just throwing it out there.
EDIT:Another thing. In that same conversation, he called GTA IV a First Person Shooter. Just throwing it out there.