Performance monitoring service Gomez has released its annual list of major websites with the best overall responsiveness as measured by Gomez over the entire year 2009. Surprise winner:, a site that uses images sparingly and pushes off large documents to PDF format for downloading, rather than trying to serve them as Web pages.

Gomez spokesman Frank Cioffi says the Lexington, Massachusetts consulting firm, which was acquired by Compuware last year, has learned an important stat over the past year. “It used to be that you had eight seconds to engage your customer before they hit the back button. Today, that’s down to two or three seconds,” due to the proliferation of broadband sites and the examples set by Google, YouTube and the IRS.

The chart below shows which mass-market sites fared the best over the year in Gomez’ tests.

The full report (a PDF file) includes mobile contenders as well. Google won best mobile media search, Best Buy won best mobile retail site, and Bank of America beat other financial institutions in mobile performance.