It's no worse than the Sonic Advance games at worst, which used cel shaded sprites on detailed backgrounds. I use cartoonish but more detailed sprites on editted photos. It captures the slightly surrealist look I was going for and it's something I'd rather not change.
I like it the way it is. Learn to distinct between your rather pompous subjective opinions and actual objective flaws. I set out to use this style, it's pointless to criticise me on it. Maybe there's something I need to fix about the backgrounds(ther almost definitely is), but I don't need to redraw them.
Sonic advance uses normal pixel art for it's sprites... You only use cel shading on 3d objects.
Although Adam is a bit blunt, there is some truth to what he says. The backgrounds don't look too bad and the Sprite art is ok but not great, but they look ugly together.
If you chose that style on purpose then you have a weird taste.