Barbarian: 687 hours. First class, played on and off from beta to about two years ago when I finally gave up on Throw Barb. I can easily say a third of the time was spent dealing with vanilla Inferno. Original barbarian was named Stonewall whom I deleted when I went through a rage quit phase.
Crusader: 95 hours. I have not played Crusader since the days of creative Thursdays or whatever when home made builds were published on the forums.
Demon Hunter: 197 hours. Currently my main class.
Necromancer: 25 hours.
Witch Doctor: 145 hours. I have not played WD since they lost pet thorns.
Monk: Three hours.
Wizard: Zero hours. Never been interested in playing Wizard.
I’ve played on and off since Beta with very long periods of dormancy. Sometimes spanning a year or more with periods of activity lasting a few weeks before going inactive for several months. Lately I get about 2-3 hours a day in during the week with about twice that on the weekends.