I could easily see both the Flash or Deadpool taking this. I'm going to say this is a draw, against any of the 4 flashes. Which I believe gives him at least enough of an advantage to even out the playing field, and get a win at least 50% of the time. However, Deadpool is a master at improvised fighting, and a master at calculated fights.

Deadpool has held his own against a lot of villains who far surpassed him with their physical and/or mental strengths. I refuse to say this as a clear curbstomp or landslide victory. However, 50% of the time I see the Flash KOing him long before Deadpool can draw this out. The Flash will run out of gas long before Deadpool and I think Deadpool is smart enough to use this to his advantage. I think the only way for Deadpool to win this is to trap the Flash somewhere, preferably in a place with a lot of objects (A factory or a warehouse or something) and simply use time to his advantage. Deadpool can teleport, granted, the Flash can run to where Deadpool is in less than a second, but Deadpool can also use the environment to keep himself well hidden and keep the Flash at a distance and in the dark. I'm going to say Deadpool at the very least could beat all of them 50% of the time.

However Deathstroke has beaten the Flash, and I know Deadpool isn't Deathstroke, and though I view the two as an even match, I don't want to do that argument. This would slow the flash down a bit (not substantially but any little bit counts). Deadpool could set this up in a cold spot in the city, maybe an industrial cooler or something.

Deadpool 1 recap