I think if you talk American distance running, Webb, Ritz, and Tegenkamp have to be mentioned. Tegenkamp getting 4th in 2007, barely missing a medal, is often overlooked. Since 2006 he's really set the tone for American born 5000m runners that they can compete on the world stage and compete with runners like Lagat. I think it was Tegenkamp's performances in '06, '07, US trials '08, '09 that inspired the times Lagat, Ritz, Solinsky, and Rupp have run in the 5k in the last couple years. Teg probably hasn't had one huge race that should make the top 10 list but he's had so many solid races in the US and Europe over the years.
The following absolutely have to be on the top 10 list:
-Ritz's American record 5k
-Webb's AR, win in 04 or 07 Diamond League, or high school record
-Kara Goucher's medal
-Shalane's medal
-One thing Hall did: I'd say Olympic Trials was probably his best moment.
-Lagat's WC double
-Kastor medal
-Meb's win in NYC or medal
-Solinsky 10k
-Something about Symmonds, Rowbury, Wheating, or Manzano's NCAA career
Honorable mentions:
-Rupp's distance double at NCAA's senior year
-German's high school 2 mile record: has raised the depth of high school running, collegiate running, and ultimately professional