Mike Lawrence makes this interesting statement:
http://www.pitpass.com/45460-Who-Are-We-To-Judge
I wonder how the readers of F1technical opine in that matter. I tend to agree with Mike that we do not have the finer information. We can compare team mates to some degree but even that is not a simple thing. When you start comparing three drivers who have been team mates at different times for instance I think it is not right to do so. You have to consider that drivers develop over time. Jenson Button for instance had a long learning curve and is probably only now on the top of his driving performance.