Our approach with campsite selection had to do with how we planned to experience the park. Dry camping within the park was not available. Yellowstone's Grand Loop has stops approximately every 15 minutes which breaks up the day. In viewing the park in 4 quadrants the following worked for us:
1. West Yellowstone allows access to the (Q1) Norris and (Q2) Old Faithful areas. Grizzly is a great RV Park. West Yellowstone itself and areas west of the park are also within reach.
2. Fishing Bridge provides easy access from (Q3) Yellowstone Lake to (Q4) Lamar Valley. It's a good campground. Not a lot of space, no campfires and the mosquitoes were at least twin engine in size. The link below provides a good picture.
http://www.nps.gov/yell/planyourvisit/fishingbridgecg.htmTetons are easily accessed from Colter Bay.