Supes: I've raced you before, Barry, I even won some of those races.
Wut? When did Superman beat Flash in a race? Flash fan-site Hyperborea says
the best Superman has ever been able to do is tie.
As for Quicksilver, most of the speedsters in the DC universe easily outmatch him in speed. Jay Garrick, Barry Allen, Bart Allen, Johnny Quick, Jessie Quick, Max Mercury.... all of them are capable of running much faster than Quicksilver.
The Marvel vs DC collection has a section of character stats in the back. The Flash's upper speed limit is nearly the speed of light. Quicksilver's upper speed limit is the speed of sound. Given, the Flash's speed has varied over the years, but at times in comics various flashes have been said to have run faster than the speed of light. According to wikipedia, Quicksilver's powers got upgraded at some point by a future version of himself allowing him to run at about five times the speed of sound.
So, really, there's no contest between Quicksilver and the Flash. Quicksilver and Kid Flash might have been evenly matched at the beginning of each of their careers, running at about the speed of sound, but Wally West went on to become the fastest speedster in the DC universe, entering the Speed Force and coming back again.