Yeah, this game is way too hard. I've beaten some hard games, but damn. I've just barely been able to get enough stars to unlock Gillius but I still need 40(!) to unlock the next character. I'm guessing most kids(who are the primary audience for this game) won't even be able to make it that far. I can't even beat most of the missions on hard, let alone expert. I'd like to give a middle finger to the people who complained that the first game was too easy. At least it was more fun as well.
I don't generally give up on games either, especially not Sonic games since it's one of my favorite franchises, but I'm about at that point.