Depends on your definition of a top player. The likes of Kevin Phillips, or even those who did it more regularly like Inzaghi were never top players to me. Nor was Darren Bent for all his goals.
Costa knows how to get goals, at least je has for one season of his career so far. However, when it's all over, he won't be looked back on as a great player in my view, he was just the guy who got the goals for Atletico/Chelsea at the time. Had to be someone, they are top clubs.
Statistics have nothing to do with my assessment of Costa. I have often spoken about how I draw my assessments from 'watching the game as opposed to reading it'. I don't draw all my opinions from what I could get from Opta data or Wikipedia. From watching Costa, and seeing what he can and can't do - my view is that he isn't a very top player.
If Diego Costa, RVP and Suarez all get the same amount of goals next season, how do you decide who is the better player? Or are they all just as good at football then?