We camp primarily State campgrounds. We have attempted to stay at some private campgrounds over the years and find most are just not much to offer us. We use KOA and Good Sam campgrounds when traveling and need an overnight and move on. We don't do Wall Mart parking at all.
We have 1 private campground we like to visit, only because they open a bit earlier in the season than most every where else, and it lets us do a new season shake-out of the camper with full hook-ups and such. But this is the only one we've found we actually enjoy.
We have stayed at a few for 2 or 3 nights, and each time we say we really miss the State Parks. State Parks just have much more to offer. Like the OP said, usually larger spaces and the setting is almost always more of a nature setting, rather than a concrete jungle with everything packed in so tight one awning touches the next trailer over.
