Big Ten: Michigan. Can't argue that--national champion, possibly the biggest fanbase in the country.
SEC: Texas. Interesting not having Georgia here, but Ewers coming back is a big story and everyone is interested to see how they do in the SEC.
Big12: What other team would you put there? Colorado has a lot of eyes on it and gets a lot of views. Also, people are going to want to play as Colorado. No other Big12 team has as much national media attention as Colorado.