It's also had a couple of sequels/remakes... including one on the SNES where you could play as these two girls!River City Ransom was one of the best NES games. It was a 2 player co-op beat-em-up with RPG elements (leveling up, stats, money, shops) and involved an open world map that you had to hunt down rival gang bosses and defeat them so that you could confront the final boss (at the eponymous rival high school, River City High) and rescue your girlfriend.
But really, it's basically Double Dragon but with RPG elements... to the point that one of the bosses actually used the Double Dragon theme. It's just been a bit more enduring than Double Dragon.