Flash has the best villains in DC, Batman has the most recognizable villains in DC. That said, Batman already had the most characters of the last game and his representation INCREASED. Not only did it increase but COMBINED Superman/Flash/Green Lantern MATCH Batman's characters. It's ridiculous.
Of course people are gonna keep asking for them because it's all casual fans know because he's showcased so much. People would be hard pressed to give me 3 Wonder Woman villains despite the fact that she has an AMAZING villain in Circe and a great anti-hero/villain in Big Barda. Before the TV show the same could be said for Flash in terms of naming villains. Before the TV show what was the last 3 Flash mainstream things? Flashpoint Paradox, the Justice League cartoons, and a 90s TV show that lasted one season. How are people ever gonna know more if all they see is one guy? People know Ares and Killer Frost now from IGAU, people are learning about Swamp Thing from I2, why is Bane and Catwoman needed to sell the Batman side of the roster when you have Batman, Robin, Joker, Harley, Scarecrow, and Ivy.