He's not in top form, but I also think that he's not helped by his team mates too.
Last year, when the season began, he was in top form and scored goals because the team used to play with pace and penetration. As the year gone, he started to slow a bit, like the team, and I think that he's far better with a lot of movements around him, and closer to the goal.
He was excellent his last year at Arsenal because of that, he played higher in the pitch, ran less, and had all the ball around the penalty box and beneficiated from Arsenal pass game too
With Moyesy he was a target for crosses only, we played too deep and too slowly. I think this style suits more to a Falcao, Rooney or even somebody like Cavani who loves to start deep.
I really think that if we manage to control the ball better, and then being higher on the pitch with more penetration than we have now, he will benefit from been upfront.
I would say that with players like Vidal, Khedira, Strootman and top wingers like Angel, he could shine again.