Most of those fancy Russian aircraft are only one off technology demonstrator prototypes like the Su47, or extremely limited in production because Russia can't afford them. Russia only has a handful of Su-35s and Ka-50s for example, and their pilots only fly about half as many hours as NATO standard.
But anyone can get lucky, a Skyraider shot down a Mig 19 in the Vietnam war, you wouldn't predict it, and it's hardly common but it can happen.
If there was a lot of F/A18s against one or two F-22s, then when the F-22s run out of missiles they will either disengage or go in for close comabt with guns.
Also considering the F-22 is quite new to it's pilots and the F/A-18 has been around for a while and some veteran pilot will really know how to get the best out of it, it's not too far out of the question for this to happen.