Didn't Treasure make that (as well as a few other slightly niche games that are awesome)?
I loved that game too, and it almost goes without saying (plus, it's been said) that it fits, with all the SHAKE SHAKE stuff and all.
I thought Treasure has always been leery about sequels but they did make Gunstar Heroes Advance so there's a possibility they'll revisit the world of Clancer (that is what is was called, wasn't it?)...
Man, that game had cool bosses...