Nothing wrong with the Mig 21
A very good aircraft in the right hands and if it has been breathed on by the Israeli avionics industry, it is pretty much as good as anything close in par the F22, Typhoon and Rafale for a tenth of the price
The F16 is nothing more than a 21st century Phantom with one engine since the yanks insisted on weighing it down with 2 ton of fancy electronics and bombing systems
The Su27 is a match and maybe more for the F15 and F18 due to its greater combat load and variety of missiles.
The Su35 would wipe the floor with anything other that the F22 (which can't fly above 40000 ft without killing the pilot), the Typhoon and Rafale if you let it get within missile range
Our CCC is probably better but the Russians are not that far behind.
The Russians have a air to air missile which is specifically designed to wipe out CCC type assets.
It would only take a few one way trips to take out our CCC and we would be blind.
Okay, Nato might out gun Russia but it is not a nato fight
If anybody went to the Ukrainians side it would have to be us and the French because the yanks under Obama haven't got the balls for a fight.
Sorry, best the Ukraine gets used to the idea of putin and his chums controlling the eastern side of the country because they ain't getting it back