Most respected: I’m not crazy enough to start that flame-fest.

Best selling: If licensed fonts count, I think Monotype wins for all the sales of Arial, Times New Roman, and Verdana that are packaged with Windows/MS Office.

For direct sales? Probably Monotype, at least now that Monotype has purchased Linotype and has a Brobdingnagian portfolio to sell.

If you want to consider hottest and most respected *newcomer* among font sources, my pick is

http://www.joshuadarden.com/

I think Linotype and Helvetica Neue need to figure in there somewhere.