My only choices are essentially O'Reilly and Autozone.
The local pep Boys converted to service only a couple of years ago.
No real difference in quality that I can tell. I try not to buy anything significant from them though... generally stuff like oil, filters, spark plugs, etc.
Our Pepboys converted the sales floor/parts department to Advanced Auto, but their service center stayed Pepboys. So we have O'Reilly, Autozone and Adavanced Auto all on the same street about a block away from each other. We have Napa and a CarQuest as well.