A while back, Dziadek1990 on Deviant Art released a character screentime analysis for season one. Within, you could find accurate to the second information on how much each pony was involved in the show. After 120 more hours of work, he has added on the 26 season two episodes. Even with the new "Twilight Sparkle doesn't need to be here" clause, she still came out way ahead. I'm not complaining though!
Anyway, check it out here, or click the graph above for the full version.