Comparing Warren Buffet's Berkshire's performance with SPX shows a out-performance of SPX by factor of 8-10 since 1993. A look at this chart reveals this clearly
Now the next steps is comparing your own performance with the SPX.
Reviewing your own performance reveals that although this performance may have been fairly met for the last 2 years, it would require careful steps to keep consistently achieving the same for the next 20 years...
2009 ROI of 279 % vs SPX 30 %
2010 ROI of 112% vs SPX 12.78%