That's what I've always wondered! I used to get into a lot of arguments about Superman vs Flash, though, a lot of people believe Superman is just as fast as Flash...
But I don't believe that. I believe that if Flash really cuts loose, Superman won't be able to keep up. And how can you attack something that is too fast for you to touch? I will admit that if Superman can get his hands on Flash, the fight will probably be pretty much over - but my counter-argument is that NO-ONE should be able to touch him.
And if there should be a ruthless Flash, one without any regard for life or consequences, one who enjoys and revels in his power - then I think a lot of the heroes (and villains) who have been dismissing the Flash so contemptuously over the past few years, are gonna be lying around, dazed and stunned, mumbling "What just hit me?"