I'd have to go with Webb still. He has set ARs at 1-mile and 2-miles, he's run top 10 times for an American at all events from 800m-10,000m. He's been ranked #1 in the world and he's won more than one race on the Euro circuit.
He is a 3x USA champion. Currently holds 2 records. 7th place Oly 1500m. 9th place WC 1500m.
At his best, he was arguably the best 1500m runner in the world in 2007.
Then I'd go with Ritz. He's set records at 5,000m. He's an NCAA XC Champion and 2x Olympic qualifier. He's the only one with an international medal (world half bronze and world jr xc). 10th place olympic marathon. 6th place WC 10k.
At his best, he was probably a top 8(?) 5,000m in 2009.
Then Hall. He's been the best American marathoner based on time since 2007. He's the 2nd fastest American ever at the marathon for record purposes. He's probably the only American in the past 20 years that we can expect to be in top 5 in a major marathon.
At his best, he is arguably a top 15/20 marathoner in the world currently.
Who's hottest right now? Hall.