The Flash has never really has a great run (ha) in video games, perhaps besides being awesome in Injustice 2.
However, there was once a plan to to have a standalone AAA game. As the excellent Unseen64 chronicle, developers Bottle Rocket, alongside Brash Entertainment and Warner Brothers planned a big, big game focused on the characters. This game would have been focused on the Wally West version of the character and it would have taken place within the first 12 months of the character getting his powers.
Based on the sheer depth this goes in, it seems that the design document and work done on this was quite vast. From bosses, enemies, abillities and ideas, this is a deep look at the game that never saw the light of day. It seems to have been a casualty of Brash Entertainment imploding, which is a shame. This could have been pretty good.