Mario Cipollini: 1943 watts. Although that's probably the max reading from possibly a minute long sprint, depends on the course. There's probably slightly uphill sprints that would have even more max wattage potential since top pro sprinters on flats are probably maxing out what they can neuromuscularly coordinate on a 53x11.

But anyway, if you know who that is, you'll know that 2000 watts is not a common max output.

Edit: Ok I was a 320 watts for 20 minutes guy a few years ago, I'm probably about 250 watts for 20 minutes guy now. I just did this workout, probably in the 500-600 watt range for the 20 second surges, and it was surprisingly hard.

He talks about 20 seconds, that's quite the length to hold 1000W+ on. Not to mention repeat it multiple times with 2 minutes of recovery, which is nowhere near enough for untrained or trained athletes unless you dedicate a significant amount of your recent training on sprints.

FWIW, I'm in a similar boat, my FTP currently is around 275W, granted I'm smaller (62-64kg), but I am still a long ways away from holding 1000W for 20 seconds.

I routinely workout with college athletes or former athletes so perhaps my data is skewed on the top end.