Neither Shorter nor Rodgers ever set a WR . They're tied in both World Rankings points and #1 rankings. Shorter holds the world's longest winning streak for the marathon, and is the third most successful Olympic marathoner ever. Rodgers bombed in '76 and never got a chance to either redeem himself or bomb again in '80, so for me that's a non-issue. Rodgers won the biggest US races eight times, while Shorter's greatest successes came outie of the USA.
I'd go with Shorter over Rodgers, but only because I think of the Olympic races as the most important. That's an iffy statement when it comes to marathons, though.
If you're talking about KK's complete career, he's obviously in the top three, and might even be #1. If you're talking about his career as an American, he might be eclipsed by DeMar just by sheer wealth of numbers. It's interesting that this is the only distance race where the USA has as many as four really great runners -- only in the mile do we have more than one!