He's got a lot of quality and I wouldn't call him a flop yet but with the quality City have up top and his injury record it wouldn't surprise me if he ends up a flop.
Soldado is the biggest flop by far so far. He's a goalscorer who doesn't score goals.
Felleini may come good eventually but he looks woeful at the moment. There's a good player there if you find the right role for him, which I would have thought would be easy for Moyes having spent years with the guy at Everton. But neither look like they have a clue what part Felleini is supposed to play in midfield.