Which index to benchmark against?

Some people suggested that I should not compare my results only against the S&P500 index, but I should compare them against a number of indexes, especially the Small and Mid Cap indexes as most of my stocks fall under those categories. I just did that analysis.

As you can see in the below graph, the leading indexes were all down anywhere from -9% to -15% in the last 14 months. During the same period, my Magic Formula Fund has returned 0.45%. So far my Magic Formula Fund is beating all major indexes by at least 10%. Not bad.

Indexes:
S&P500 index (S&P500)
S&P 600 Small Cap index (.SPCY)
S&P 400 Mid Cap index (.IDX)
Russell 2000 index (IWM)