Flash just doesn't have Super speed He could Steal Speed and turn his opponents to statues once he steals the z fighters speeds Superman can whack away at them or he could infinate pass punch them. He could also phase through objects, Dimension travel and he could regenerate he is so underrated.
In all honesty, DB doesn't have an endless amount of stories in it. It's set in one story. There's no 100 versions of Goku. That's why comparing comic characters to other characters tends to be unfair. There's times where I've seen the Flash go out like a bitch. There's other times he looks like a God. I'd think a better fight to compare would be like Vincent from FF7 Vs. Dante from DMC.
A bunch of guys made a fan-made 2D fighting Dragonball Z game with a similar look to Street Fighter 3rd Strike and DarkStalkers and it looks pretty damn amazing. I can't properly link the video here since I'm on my phone but you fellas can look the video up on youtube. The game is called Hyper Dragonball Z