For us it's Grizzly RV Park in West Yellowstone. We usually end up there at least once sometimes twice a year. Great base camp to unload the Jeep or the Harley and take off for the day. Love it.
We stayed at Fishing Bridge and found it serviceable It was to under go new electrical after we left!
We basically use the campgrounds as a bedroom setting when at a major NP. We do not go to sit in the CG with so much to see! Drag in at dark and leave at dawn, lol!
Saying that, it depende on your rig, time in camp, and just what you are there for when making your own choices!
Your in Yellowstone...hard to go wrong with any spot
We have stayed at Canyon, Madison, Bridge Bay and Fishing Bridge. We don't go to Yellowstone for the camping experience. We go for the Yellowstone experience. We like Canyon the best as it is close to good wildlife viewing. Madison would be second as it has good location to thermal sites and outside the park services. Bridge Bay was ok in a pinch but would only go there if others were full. Fishing bridge is fine for us as we don't do anything in the campground other than sleep. So havin full hookup would be the only reason to stay there.