Since I'm bored, I took a look at the list of current NFL HCs and checked if they had any college HC experience.
Arizona: Arians, Temple 1983-88 (27-39 unofficially, roster violations, 0 bowl games)
Atlanta: Mike Smith, None
Baltimore: John Harbaugh, None
Buffalo: Doug Marone, Syracuse 2009-12 (21-17, 2-0 in bowl games)
Carolina: Ron Rivera, None
Chicago: Mark Trestman, None (CFL head coach)
Cincinnati: Marvin Lewis, None
Cleveland: Mike Pettine, None (HS head coach)
Dallas: Jason Garrett, None
Denver: John Fox, None
Detroit: Jim Caldwell, Wake Forest 1993-2000 (26-63, 1-0 in bowl games)
Green Bay: Mike McCarthy, None
Houston: Bill O'Brien, Penn State 2012-13 (15-9, no bowl games due to NCAA sanctions)
Indianapolis: Chuck Pagano, None
Jacksonville: Gus Bradley, None
Kansas City: Andy Reid, None
Miami: Joe Philbin, None
Minnesota: Mike Zimmer, None
New England: Bill Belichick, None
New Orleans: Sean Payton, None
NY Giants: Tom Coughlin, Rochester Institute of Technology 1970-73 (?), Boston College 1991-93 (21-13-1, 1-1 in bowl games)
NY Jets: Rex Ryan, None
Oakland: Dennis Allen, None
Philadelphia: Chip Kelly, Oregon 2009-12 (46-7, 2-2 in bowl games)
Pittsburgh: Mike Tomlin, None
San Diego: Mike McCoy, None
San Francisco: Jim Harbaugh, San Diego 2004-06 (29-6, 2 Pioneer League championships), Stanford 2007-10 (29-21, 1-1 in bowl games)
Seattle: Pete Carroll, USC 2001-09 (97-19 unofficially, 2x National Champion??)
St. Louis: Jeff Fisher, None
Tampa Bay: Lovie Smith, None
Tennessee: Ken Whisenhunt, None
Washington: Jay Gruden, None (AFL & UFL head coach)
8 out of the 32 head coaches have college HC experience, I'd say only Carroll and Kelly were extremely successful, followed by Harbaugh, Coughlin, and O'Brien (considering the circumstances).