You can't get much better than SoR2 for a beat-em-up. Final Fight isn't quite as good IMO, but then that started a tons of other Capcom beat-em-ups which bettered it -- Alien vs Predator, Punisher, Captain Commando, etc.
RCR is damn good, but for different reasons (the power-up elements). Though as a pure beat-em-up, it can't really touch any of the games above.
I totally disagree. Final Fight is boring as hell. After you kill the first two ore three guys you've used every move in the game meaning that the next 45 minutes is just the exact same shit over and over again.
In the Kunio games you can do sooo much more. You can sit on the guy and beat on him, you can pick him up and throw him down the street, you can hold him from behind while some other guy beats on him. I think you can even play catch with a human by throwing him between P1, and P2 over and over. You can even, oh my gosh, *run*. Imagine that, Final Fight.
Now, not all this stuff is in RCR, but RCR is a very early game in the series. The first, maybe, not sure. Check out Kunio-kun Tachi no Banka for Super Famicom. That one is great. Also, that one pit fighting 4 player one, and the running one that is a lot like Crash and the Boys.
Shit, even Ganbare Dunk Heroes, a friggn Basketball Game, has more fighting moves in it than Final Fight. The Kunio series is so great. One of the very few Famicom era series I can still actually enjoy.