I'm going to knock off Bruce Lee and Bolt.
A lot of talk about Bolt, and mention of the fact that he's a specialist, it docks him a point. The two most dominant runners in history, IMO, are Scott Jurek and Kilian Jornet.
Jurek is a legend. You like continued dominance? Here's a breakdown of his ultra races:
-7 straight Western States 100 (mile trail run) - set course record, twice sprained his ankle, once during the race, and once a few days before... still won. (only ran these 7 times: winning all)
-Won the Badwater Ultra (135 miles from the Death Valley to Mt Whitney), setting a course record, and just weeks after having run a 100 miler...
-Set the US Record (2nd overall World) for all-surface distance in 24 hours (165.7 miles)
-Won 3 straight Spartathlon Ultras (153 miles), grabbing the two fastest times
Yiannis Kouros (honorable mention, as he holds many distance records).
- More than 30 wins in major Ultra events
-Appalachian Trail speed record, going the harder direction (no other speed record has ever even been attempted North bound) while dealing with a knee injury and the worst rain month in record through VT.
Kilian Jornet is another ultra runner who also is an accomplished, record setting ski-mountaineer. Kilian is arguably the most dominant runner today. His most recent accomplishments include:
- 3 straight Hard Rock 100 wins (arguably the hardest of all ultra races), setting the course record in each direction the first two years, then posting the 3rd best time this past year, deciding to stick with another runner to finish together instead of attempting to set a 3rd straight course record.
- Over 14 wins, 3 championships, and 2 champion of the year titles at the Skyrunner World Series and Championship, including the Ultra Trail Mont-Blanc, Marathon Mont-Blanc, and Vertical K.
- Western States win
- NorthFace 100 win (course record)
- Mount Marathon Race win (course record)
- Ultra Pirineu win (course record)
- Many other wins in various trail race. A non-first place finish is extremely rare, and I don't think he has ever finished worse than 4th at any major race. Just about every random run he's done in the US has set records, highlighted by the Hard Rock races, but also including things like:
- 165 mile record time running around Lake Tahoe
- record ascent of the Mt. Sanitas Trail in CO
One thing that makes Kilian unique is the different running/mountaineering projects he is always active in. In addition to the normal races, he also has set records running/ski-mountaineering many of the worlds prominent and or difficult mountains. This includes:
- Mont-Blanc Traverse
and the combined Ascent/Descent for the following:
- Mt. McKinley
- Mont-Blanc
- Matterhorn
- Denali
- Aconcagua
- Kilimanjaro
An example of how crazy the guy is: He did a 23 hour run/climb up Grandes Jorasses (13,800 ft) then ran the Mont Blanc Vertical Kilometer the next day, finishing 7th.
If that isn't enough, he's also won a whole lot of ski mountaineering races, including 1st place finishes in Spanish, European, and World Championship events.
No one in the world moves faster over the most gnarly of terrain. Watching him run down super steep rock faces is unreal. My legs cramp just watching him run up super steep scrambles.
Usain Bolt may be the fastest sprinter on the planet, but Kilian is just as dominant, but a far more diverse athlete. Dominating in a very specialized field is one thing. Dominating in a wide variety of races in multiple sports is a whole different ballgame. I look it like this: the only race that Bolt could probably win against Kilian would be short and on the track. Any other distance, venue, or involving anything other than shoes and it's not a contest.
And as for mind-boggling quality, sure, running as fast as Bolt does is crazy, but trying to break records at different sports where the duration sometimes lasts 40+ hours ( or 46 days for Scott Jurek's AT record) is again, a whole different level of mind-boggling "how do that do that". The mental challenge of these crazy ultras is insane.
I do think it would be cool to see some of the Kenyan sprinters and marathoners compete in ultras and mountain runs, but I'm sure those eyeing the Olympics probably wouldn't ever risk going off trail. But that's just another credit to the mindset of ultra-runners. They'll run anything, anytime. They don't worry about potential injuries.