I forget who said this but Rayman Origins doesn't look bad on the 3ds...In fact all the graphical effects and such seem to be in place... ( just downloaded the demo)...
I think the thing you think looks bad is the screen resolution, unfortunately the screen doesn't have that great of a resolution so it looks quite blurry, and the sound effects I admit are atrocious....As far as the graphical powers though it looks fine to me.
I can only imagine what the castlevania is gonna look like on this, wowzers...