AA Flagship Dining is only open to AA F passengers. It's hard to compare a F product since UA is discontinuing it. Polaris lounge (with all its shortcomings) will still be the only business lounge with table service menu dining. The only thing comparable in North America would be AC Signature Suite. BA JFK Supper service is self-served. Of course, one can argue about the actual quality of the food between Polaris, Flagship, Skyclub, Centurion, etc.