Looking over the top 50 best sellers at Myfonts.com earlier this week, I was impressed at how many were sans serif. The exceptions were #4, a Japanese typeface, #23, the only serifed font on the list, and six script fonts at #s 28, 29, 33, 38, 41, and 44. (If you check the rankings, they will undoubtedly be different because they change day to day.)
My selection of san serif fonts is shown here, though some of my decorative fonts are also sans serif (see here). None of them are even in the top 5000 of fonts at myfonts.com. (I am not sure how many fonts myfonts has--it keeps increasing and must be at least 40,000.)
One san-serif font is so popular that it starred in a movie. You can see it on youtube here.