I didn't think anyone "rated" Bendtner so I don't think he can be that over rated. He his the worst striker to ever pull on an Arsenal shirt though, and is an embarrasment to the club.
We only have a few players that the media actually "rate". I would say our highest rated players are Cesc, Gallas, Toure, RVP, Ade and Arshavin. Of those, I think it's a tie between RVP and Ade. Both can be brilliant but more often than not can be totally ineffective. Thery are just plain "OK" but are often referred to a world-class, which is what I call over-rated.