Some of you people are making such idiotic generalizations. To say that all it takes to be an RPG is to play the role of a character. I can play the role of Lightning. Or Hope, or whatever (haven't played FF13). Or, ya know, I could play the role of a plumber, saving a princess. Whoo hoo, I can play the role of the plumber! Thanks, Super Mario Bros! Or I could play the role of Zangief, bravely battling my way through hardened warriors, suffering minor setbacks all the while, but in the end being victorious and glorified by all of mother Russia! Character progression at its finest!
On the flip side, to demand total choice is also stupid. Yeah, in ME you can't really change your ultimate goal. Go ahead and play up your PnP RPGs. Decide that instead of rolling a ranger, you'd rather be a cobbler, and refuse to do anything but craft shoes. See if you get invited back. While yes, the flexibility given by having a human think of consequences to your actions on the spot is much greater than a video game developer trying to think them out in advance, your DM DID think out a goal in advance, and is going to steer you toward that goal however you choose to go about it.
I believe that the defining characteristic of an RPG is the ability to make a choice, and have NPCs respond to it in a way that affects things for more than one battle. In Halo, you can choose to attack from a different angle, but once that battle is over your choice is forgotten. You can choose how to upgrade weapons in RE4, but I don't think "dying faster" can really be called NPC response by a sane person. In ME you can be selfless martyr, or a mercenary dick, and be treated differently. You can fall in love with (almost) your pick of the NPCs, and have the NPC "love" you back. In FF8 you can let Squall sink gradually into a depraved vigilante mindset before being redeemed by a passionate romance with Selphie. No wait. No you can't. You can uh... decide whether you want him to summon a fire demon, or a thunder bird. Hot balls whoo. I'm not saying all JRPGs are undeserving of the "RPG" part, but the FF series is very lacking on roleplaying. I know in the end I have to fight Kefka, but can I at least have the pretense of doing it to replace him? Can I have Barrett refuse to stay in my party after I say I'm only fighting Sephiroth for revenge? Can I have SOME nominal choice?