It's hard for me to watch the London 2012 final here:
https://www.youtube.com/watch?v=YKEOjWEzVGs
... and not come away thinking 'the great man' (as one of the announcers calls Rudisha) is not the best of all time. Rudisha ran 1:40:91 in that race, a new world record—opening with a 49.28, and coming home in 51:63.
• He led that race from gun to finish.
• His stride never broke. His shoulders never came up. His motion remain unchanged. Pure elegance and command. And all of that while the rest of the field did their best Emil Zatopek (another of my track idols) form impressions... struggling to reach the line.
And, speaking of the field...
— Here are some superlative bits about that race from
https://en.wikipedia.org/wiki/David_Rudisha
"Rudisha's competitors all ran exceptional times. Sports Illustrated's David Epstein reported that the race "is best told, perhaps, in 16 letters: WR, NR, PB, PB, PB, NR, SB, PB." The silver medallist, Amos, had to be carried from the track on a stretcher after setting the world junior record and make him only the fifth man in history to run under 1:42, something Rudisha has now done seven times. "With Rudisha breaking 1:41, two men under 1:42, five under 1:43 and all eight under 1:44," noted the IAAF, "it was the greatest depth 800m race in history." Every competitor ran the fastest time in history for their placing. It was the first time in international 800m history where every competitor ran either a personal or season's best. The time set by the eighth-placed Andrew Osagie, a personal best of 1:43.77, would have won gold at the three preceding Olympic games in Beijing, Athens and Sydney."
Now, having said all that, I looked for decent video of Wilson Kipketer's PR 1:41:11 race at Cologne in 1997. I couldn't find a good clip. However, some other posters mentioned his indoor WR of 1:42:67. Here's a clip of that race, run on what I swear looks to be the track with the tightest turns I've seen:
https://www.youtube.com/watch?v=Rp-IDEo4eh8
Kipketer's WR there stands today. It was as dominant a performance as Rudisha's was in London 15 years later outdoors.
So far as greatest ever, I land with Rudisha. As with all these discussions though, a Kipketer vs. Rudisha race outdoors would be for the ages. (With Rudisha's height, I think Kipketer carries the day indoors in a head-to-head.)