1980 UGA is an example of a lucky NC team that wasn't that great. They snuck by several opponents and caught ND on a bad day in the S Bowl. They did have a good defense and a decent running back. That team would not survive another credible opponent IMHO.
Another question is how often the "best team" wins the playoff, presume you know the actual best team. Every team has a bad day, fluke fumbles, tipped INTs, etc.