That's funny, I hated Canyon CG when we were there last year. A lot of sites are heavily sloped, way beyond the normal "need a few leveling blocks" sort of deal. Well, at least many that we saw. It is nice and wooded and many sites are private, but the CG is so spread out and hilly that it doesn't make for easy access down to Canyon Village, the office, showers, etc. The showers were good there, though, as I recall.
Grant CG was less private (sites aren't as wooded), but I liked it better than Canyon. Also nice to be able to walk down to the lake and watch the sunset. Showers there are a bit up the road, back toward Grant Village. A longish walk or an easy bike ride, but the road can be busy. I don't get why they put the shower building so far away from the actual CG. Annoying.
My two favorite Yellowstone GCs are Slough Creek and Pebble Creek, although they are first-come, first-served. Much more "rustic" and they make great jumping-off bases for before-dawn wildlife viewing in Lamar Valley. From Pebble Creek you can do a hamburger run to Cooke City for dinner, too!