Some of the more popular pundits are visible enough that independent researchers compile comparative reports on them versus the market in general. Their are many on the (annoyingly loud) lightning rod that is Jim Cramer (e.g. http://www.scribd.com/doc/15672032/Investing-in-Mad-Money). Other people have much more precise records for comparison: http://finance.yahoo.com/q/ta?s=BRK-A&t=my&l=on&...
In a similar vein, WSJ had a very clever "dartboard contest" for years. (http://www.investorhome.com/darts.htm) Unfortunately, it requires a subscription to see the results. You might find it interesting if you have one.