In the past 15 years, USA 800m running has had a few interesting competitors to consider in this debate:
Brazier: World Champion in American record time, seems to have the highest ceiling of US 800 meter runners. However, has been injured and not qualified for the Olympics. This year will be a compelling story if he can get back to top form.
Murphy: Olympic bronze, has qualified for multiple other finals (both WC and Olympics) but not close to any more medals.
Symmonds: WC silver and Olympic 5th place in deepest 800m ever. Dominated domestic scene, qualified for Olympics twice.
Berian may have been in this conversation had he stayed healthy, and Hoppel could still join this group.