This is hard to answer... My answer is he could've done better, but in reality the hype might have created unrealistic expectations...
I mean, he came here as a soon-to-be Messi demigod kind of player, but now it's clear he is still far from that, so according to those expectations, yes, he could've done better... But if the hype wasn't exaggerated and the expectations were kept grounded his first season could be deemed decent enough...
He became a victim of his whole merchandising persona, he came a superstar and is just understandable that people expect him to be one... Had he come here as a very promising youngster to be polished into the best player of the world in due time (which is my opinion on him), things would be a lot different...