Concur with Grizzly. It ain't cheap either but it's only a few blocks from the park entrance and walking distance to everything in town. Better make reservations as soon as you can...it gets pretty full.
On the west side I stay at Grizzly and have reservations there for a month this summer. They don't start assigning space until May but will take a on-line reservation now. This park is what one might call very finished i.e paved streets and sites, beautiful landscaping , etc. They were adding to the park when I left last September - mainly cabins I think. On a much less formal basis , I like Yellowstone Edge which is 35 miles north on 89 from North entrance. It is very friendly with great views sitting along side Yellowstone River and mountains in background. This park puts you in good position to go in north entrance and do the sites up in that end of park. They have a community fire pit each night and everyone gathers around to chat and eat great Wilcoxsin ice cream.