I don't know if there were side-scrolling beat-em-ups BEFORE Double Dragon, but if not, talk about being a trailblazer! Remember how popular this genre was in the arcades and living rooms of yesteryear?! It's the exact same concept as a Mario game (some asshole kidnaps your girlfriend), except this time, there's KARATE. And dragons! Metaphorical dragons, but, still, that's hardcore!
I never really played the second and third games for more than a couple of minutes apiece, so I've got no right to say much about them except: if they're as good as this, then chalk up another spectacular trilogy for the NES. Double Dragon is a four-fisted, golden age good time.
Even the movie's got its merits. A few.