There are a couple of other sites--can't remember if you have to buy the hard copy to use them or not: Woodalls and Trailer Life.
I'm a relative newbie and would recommend you invest in the hard copy of Woodalls. I think of it as the "bible" of campgrounds and parks. This year you can get a West version and an East version, and I suppose you can still get the "entire continent" version. I bought this year's west version to replace my two year-old entire continent version.
There are two bibles: Trailer Life's Campground Directory and Woodall's North American Campground Directory. Some folks use one, some folks use the other. Both provide you will detailed CG descriptions and both rate the commercial ones and some of the publicly owned ones for quality. Both describe their rating systems. I for one have used the Trailer Life directory and have found it reliable and am used to its rating system. I am sure that Woodall's would have been as useful if I had bought that.
Tho websites are useful, I suspect you will find the hard copy directory's much more useful. They can be carried in your vehicle and can be consulted on the road. Believe me, you will definitely find this very useful on more than one occasion.
You can find these publications in most RV stores, and in large bookstores in the travel section. They cost about $20. Good investments.