Rosberg did well, Schumacher did better. Yeah, you need a bit of luck to pull it off after starting 19 positions behind your teammate and doing one pit-stop more than him, but it would be more than unusual to manage to catch up with a guy driving the same car who made no mistakes just because you drove 10 laps less on hard tires.
Rosberg defended against Vettel for one lap (passed on lap 3), had no pressure on lap 4, then Alonso and Ham on his back on laps 5 and 6, got passed by both by laps 7 and 8, free lap 9, passed easily by Vettel again on lap 10, then Pit on lap 11, followed Massa between laps 13 and 17 (Safety-car), who he passed, had Massa on his back until lap 22 before he created a one second gap which he maintained pretty consistently until his second Pit on lap 30. Had a more relaxing time until lap 36, when Schumacher got within one second of him and the rest is history.
Schumacher had a busy opening six laps, with passes past slow cars and his first pit stop, then caught up with Barrichello by lap 10, passed him on 11, then Pit and SC until lap 17, fought with Button between laps 18 and 21, then had Sutil in front of him at no more than 1-1.5 seconds between laps 23 and 33, who was hard to pass because of his top-speed, caught up with Nico by lap 36 and had to race him until lap 42.
So really, Rosberg lasted in front of Vettel, Alonso, and Hamilton two laps longer than it took Schumacher to get past the really slow cars. Then Massa-Rosberg was a nice battle to follow, but Sutil-Schumacher was pretty balanced as well, seeing how FI had beaten MGP in the last two races and the track is one that has favored FI historically. Not to mention Schumacher did four laps driving against Button, as in half as much as Rosberg did actually fighting against Vet, Alo, Ham.
In conclusion, I don't think it's fair at all to say Rosberg's drive was defined by fighting against the top cars, while Schumacher's was defined by getting past much lesser opponents. Both drove against some good cars for almost half the race and Schumacher got the better of it all because after a challenging race, even if he was aided by a better strategy. If starting last and finishing in front of your teammate does not weigh enough to say that his performance was better than his faultless teammate's on the day, then I don't know what does.
P.S. Other than that, DRS and tires clearly reduce the importance of qualifying well. Button, Webber, Schumacher & others have shown it on several occasions.