I don't think I'll aim for bullet hell, I want non-asian to be able to play it too
I can't even beat the first stage of most bullet hell games and I just die and die and die and die. No fun.
My inspiration so far is Raptor (a PC classic), Raiden and Xevious. The classics, not the sequels. However, I've played Kenta Cho's twin stick games and some Geometry Wars clones (I don't have an XBox) and I really enjoyed them.
Thus the dilemma