Yeah, I do recall Riot Zone being a pretty boring game. Too bad the PCE never had a real quality beat-em-up in the vain of Streets of Rage or Final Fight. I mean, I can't think of single title other than Downtown Nekketsu Monogatari (River City Ransom) that one would consider to be a good beat-em-for the PCE.
Edit: Oh wait, Double Dragon II for PCE wasn't half bad.