Some of u are seriously underrating Benzema here IMO.
His mentality might be an issue, but there is no doubt he's an elite talent. You just have to look at his CL record to see the kind of talent we are talking about here. He's been banging them in and tormenting top class defenders(still remember his performance against Vidic and Ferdinand) in that competition since his teenage years - very few players are capable of doing that.
He's one of the most complete forwards out there - equally effective in a counter attacking team or a possession based team. Even in an up and down season like last season, only Iniesta provided more assists in the league than him. He's a creator and a goalscorer(left foot, right foot, head - no problem); about 20 assists, 20 goals last season.
He should be a far better player than he's at the moment though, but let's not forget Madrid are one of the most difficult clubs to play for. Anelka left us as a quality young striker and totally lost his way over there. Most of our super stars in the Wenger era would probably not have had nowhere the same impact for Madrid as they did for us.
Wenger can develop Benzema into a world's top 10 player IMO. We are not getting him though.