Just my opinion, and granted I don't pay nearly as much attention as I used to, but I think that right now is about as equal as I can remember all the defenses ever being. These things seem to run in cycles. For a long while press teams dominated. Then the zone became the "it" defense (though not for long). Now it seems that M2M is in favor. I think alot of it has to do with coaches noticing certain teams having success running a specific D and rush to try to copy that team's formula for success. It kind of snowballs from there. Then someone will break the trend, start winning big with a different D and the rush to copycat them begins.
I will say from personal experience that it's possible to win with ALL the defenses and at least three of the four offenses (I've never had a FB team, even after all these seasons). I've won NC's running these different combinations: Mot/Man, Flex/Zone, Flex/Man (2), Tri/Man (3), Mot/FCP, so again, from personal experience, any and all of the O's and D's are viable with the right personnel. I guess what I'm getting at is, while one offense or defense may seem dominant (okay, except for the press, which even CS admitted was way too strong way back when), they all can all be won with and won with big. Just my two cents worth.