Sadly, side-scrolling beat-em-ups are one of those games that got pushed away from the mainstream audience once 3D became the standard. Like vetalfox said, get the SoR Remake if you haven't already. While I don't mind 3D versions of the genre, they simply don't feel the same.
Dragon's Crown seems to be the closest thing to a 2D beat-em-up, but I have no idea when it will get released.