The flash is fantastic.
First off, there are a number of them.
You have Barry, the second flash. although, also first... yeah, comics. The actual first is Jay Garrick of JSA, and golden age comics. The winged helm guy. Barry is first modern flash, with red suit.
Barry is a CSI agent which is great for stories. and he is more of a hardass on crime. Hates the rogues.
Second is Wally. Wally is probably the more known, and loved among most people. Although a few creators, Joeff Johns, has a Barry hardon, and keep bringing Barry back.. wally is married, and the bro. Hes the one that is more chummy with the Rogues, and the Rogues respect him.
Then of course an entire extended family. Bart, Jessie, etc.
The Flash is not crazy. Another good thing about him. Batman is insane. it hard to write good Batman without this fact becoming a problem. only casuals don't notice it, as you only get bits and pieces. But when you read comics and start noticing a habit of dead Robins, going out of his way to save the Joker, etc.. Or Trillionaire spending 200billion a year to beat up petty thugs who need cash to feed their families.. Batman is not a hero, the guy is a madman. (times the flash has gone evil and nearly killed all his friends? 0, times Batman has? constant. every minute of everyday.)
The other thing about the Flash is the dude has the best line of villains in comics. The Rogues. They even have a fucking name. These guys should have a movie of their own.
Basis of stories for the Flash. This is a good thing, and part of the problem. The Flash is super op at times. Literally capable of anything. One minute the Flash is having Buck Rogers/Adam Strange space adventures. Because he can literally dimension hop by shifting speeds to entire new realities. The next minute hes fighting The Rogues doing bank heist.
So, you have The Flash as a classic adventurer. Going on fantastic trips. you COULD make a Flash movie like this. Flash gordan, fantastic voyage, John Carter on mars, wizard of oz, gullivers travels, type movie.
Or you could keep it simple, and make it more of a Earth adventure, and just keep the powers more grounded.