How to develop games for Xbox Live Arcade?

I was curious to know if there was any actual first-hand experience in doing such a thing. Could you make a game, for instance, in flash? Would the Xbox take kindly to “web-based” games? That being, a game online that would be able to be played with the controller? Or is there some kind of grand computer language I’d have to learn in order to really make a game well?

Going back to “teh schoolz” and trying to figure out if I want to learn software or hardware… meaning, could I make video games and apps or should I instead learn how to make hardware gadgets and the like?