A case can be made for Million Wolde, winner of the 2000 5000m. He hadn't done much prior (compared to other names bandied about on this thread): 3rd at the WIC in 3000m was his only title prior. He was a 7:32 / 12:59 guy. To be fair, he did follow the gold with a silver at the World Champs 5000m a year later.
It's silly to hear Niyongabo mentioned on this list. He was the #2 1500 runner in 1994 and either #2 or #3 in 1995 and 1996. Part of his entry in the 5000m was also to let his countryman run in the 1500 if I remember the story correctly.