What’s the best beat ’em up of all time?

Amid the great Wii, 3DS, and DS drought of early 2011, I’ve been revisiting sprite-based classics, mostly on my backlit GBA “Special.” One I’m particularly fond of: River City Ransom EX (original also on WiiWare).

Thanks to its genuinely funny script (“Cool it, Bro!”), diverse combat, and RPG-like leveling, I think it might be one of the greatest beat ’em ups, ever. Although the characters are likable, the story arch doesn’t quite pull me in like other beat ’em ups. Either way, a sequel is in the works.

That said, what would you rank as one of the most playable beat ’em ups ever, particularly ones that stand the test of time? River City? Turtles in Time? Streets of Rage 2? TMNT on Game Boy? Something else?