I haven't played Castle Crashers, so I'm hardly qualified, but even if I had played it, I'd probably still give Streets of Rage 2 the edge simply b/c of the nostalgia. The game was absolutely the pinnacle of beat-em-ups IMO. I've beaten it literally 100s of times and it still pumps me up. Nothing is more memorable to me than entering the first boss screen when the music cuts out and all you hear is rain. Then you move closer and the down right nerve wracking boss music kicks in and you're surrounded by baddies. Gaming bliss.
(Streets of Rage 3 was actually a big step forward mechanically, but the difficulty curve was way too brutal and the music didn't match up.)
My Top 5:
Shadow of the Colossus, Metal Gear Solid 3, Shenmue, Skies of Arcadia, Chrono Trigger
My 2 nex-gen systems: PS3 
and Wii 
Prediction Aug '08: We see the PSP2 released fall '09. Graphically, it's basically the same as the current system. UMD drive ditched and replaced by 4-8gb on board flash memory. Other upgrades: 2nd analog nub, touchscreen, blutooth, motion sensor. Design: Flip-style or slider. Size: Think Iphone. Cost: $199. Will be profitable on day 1.
