Flash, Impulse and superman are faster than the Martian Manhunter, everyone else with superspeed is either equal to him or beneath him in speed.
The martian manhunter is very close to superman in most of supes abilities, physically and through the use of abilities like speed and toughness, only a few people could match or exceed Martian Manhunter.
Using his fine tactical mind along with superspeed/reflexes,intangibility and creative shape-shifting he could win against flash in a battle.