The SU-27 has its advantages, and I think that in a combat situation between the SU-27 and the F-16 the SU will probably be victorious. But the SU-27 also has its flaws. Most of them (like the thrust in comparison over its weight and its form) was fixed in the making of the SU-37 SuperFlanker. The SuperFlanker would probably be a good matchup with the F/A-18E/F Super Hornet these days. But in a private view of the matter I think putting up aircraft in a physical matchup would not be fair. The machines has to be more and less on the same scale, but I think that its due to the pilots training and where he/she was trained that gives a difference.
You can't compare the F-22 to anything, currently there is no aircraft like it. It would probably not be involved in dogfights that easily and long range is the most effective these days.
As for the Cobra maneuver, it is not involved in any tactics and is simply a way to show the power of the Flanker and SuperFlanker's engines and flexibility.
When this maneuver is performed most of the body of the aircraft is in sight and for a few seconds it is an easy target for an enemy aircraft.
But it can have its advantages. When being followed by an enemy aircraft this maneuver with help the pilot to reduce speed rapidly.
For more information about the Cobra maneuver go to this URL: http://aeroweb.lucia.it/rap/RAFAQ/cobra.html