It's not just 'a' RPG, it's _the_ RPG. It was the first one to use a real skill system, the first one that allowed different ways to solve a problem (You could, for example, pick a lock, or if that didn't work use a crowbar on it via your Strength stat, or you could use plastic explosives via demolitions, or you could just shoot the damn thing with a Law Rocket if all else failed) There were no 'classes', the entire game was skill based - with numerous different types of gun of the same model with different stats and different ammo types. Pretty much standard today, but highly innovative in 1988 when the game came out. It also had a completely persistent world - also one of the first games to have that. Needless to say, it's one of my favorite games ever. I still play it. On a DOS emulator. On my Droid phone. Go figure.