I agree about RV Park Reviews. You can read reviews by campers that actually stayed at the CG in question. And its free. Each CG listing starts with what amenities are available and what the reviewer paid, along with a grade from 1 to 10.
That's how I found Grizzly RV Park in West Yellowstone, MT. Its about 3 blocks from the west gate of YNP, has grocery stores that compete, the Grizzly and Wolf Discovery Center (private with an admission fee), but about as close to either animal as you'd want to be.
Retired and visiting as much of this beautiful country as I can.