2D Action Sidescrollers for PSP

I've been playing the Castlevania games on PSP (Symphony of the Night, Chronicles, Dracula X Chronicles), and I still want more side-scrolling action goodness. Any recommendations? I'm from the US but living in Japan, so either region is fair game. Thanks!

Mega Man Maverick Hunter X and Ultimate Ghosts n Goblins come to mind but neither of those are really like the Castlevania games. They are still very fun 2D sidescrollers though.

Prinny: Can I Really Be the Hero? and Prinny 2: Dawn of Operation Panties, Dood!

Mega Man Maverick Hunter X is a pretty decent remake of the greatest game of all time. Mega Man Powered Up is pretty sweet too.

Mega Man Maverick Hunter X looks really interesting. I've never actually played a Mega Man game (I know, I know!), and it's only ten bucks on PSN. Thanks for the recommendations.