I think ME2 is a RPG. First off you do receive skill points, level up and can customize your character and squadmates with specific skill sets weapons and armor. It may not be as in depth as other RPGs but it's all still in there. Second you have a map and can travel to hubs, talk with NPCs, shop, complete side quests and open up more of the map as you go along. Rather than treasure chests there are safes and computers that can be accessed or hacked. On occasion you also come across weapons and upgrades in certain missions.
Then you have the FPS (or rather TPS) side of the game which is basically the game's combat system.
So I would consider ME2 to be a RPSG or a Role Playing Shooter Game, much like Fallout. While Fallout focuses more on the RPg elements, ME2 focuses more on the combat. I have really enjoyed both games because of how the successfully mixed the two genres.
