To me, an RPG is just that... a ROLE PLAYING Game. Where you take on the ROLE of a character and PLAY him (or her) through a GAME. To me a ROLE is all about character and the choices you make defining them. Is your guy a jerk? Does he make the galaxy and those around him miserable? Is he a great guy? Does he help out everyone and leave them all with warm fuzzies? It is these interactions with the people and the environment around your character that defines a ROLE. By this definition, I think ME2 qualifies—in spades.
Since when does a freaking inventory—a list of crap your character carries—define a genre. Maybe it's a matter of semantics. Maybe inventories and skill lists are the defining thing most people require in their RPG. Fine. Whatever. So call ME2 a 'Story Shooter' or a 'Cinematic Actioner'...but honestly, I think that heavy inventory games should be the ones changing their names to something more descriptive of what they are—"Inventory Managment Simulation".
To a lesser extent, this also applies to skills. People are commenting on the 'drastic limitation' of skills from ME1 to ME2. Oh come on. Do you really need individual skills for First Aid and Medicine and Electronics and Decryption. I for one was glad that computer hacking and security bypasses could be done by your main character—not requiring you to ALWAYS have a tech expert with you in all situations for forfeit even a CHANCE of opening something. And again, skills do not define a ROLE nearly as much as the choices that character makes. They are a means to an end, nothing more.
And for those people out there who think that the 'story' aspect in RPGs need to be less of a 'straight line'...again I say, give me a break. The ME games are like playing within a movie. That is the appeal of them for me. To turn it into something like Fallout 3, where you wander from place to place shooting things and taking their stuff greatly reduces the dramatic impact of a story. Again, if THAT is what defines an RPG to folks, then I'm glad ME2 isn't one and maybe it should change its name. I could care less if I am 'railroaded' down a specific chain of events, as long as I get to make the story along the way suit me and my own aesthetic tastes—to feel as if the hero of the story is making the decisions 'I would make'. That is what immerses me.