We used to do the commercial parks too, like KOA, etc.  We always had the impression that state parks didn't have much to offer and only the more inexperienced campers stayed at places like that. 
Well, not true.  Now the only places we stay are State, National and Corp of Engineers parks.  They are well maintained, generally offer electric and water and a dump station.  Some even offer full hook-up.  The scenery is beautiful, good hiking trails, fishing, biking, and walking.  Try to find that at a commercial park.  Prices are a fraction of the cost of commercial, seniors get half price at National and Corp. parks.
A little defense though for KOA.  On our trip through the plains states last spring we found that KOA's were the best choice, prices reasonable and had full hook ups.  This was through the states of SD, MT, WY, CO, TX.  Although they were not as picturesque as other parks and the sites were close together, it did offer the best alternative for what we needed.  Out longer stays were at national parks like Glacier, and Yellowstone.