Back in the Golden Age of comics, large teams of superheroes were the exception, not the rule that they are, today. Other than the Justice Society of America in 1940, teams were mostly comprised of non-powered characters, like the Blackhawks in 1941 or the Boy Commandos in 1942 fighting the Nazi threat.
The JUSTICE LEAGUE title was not launched until 1960! This led to the Fantastic Four in 1961, then the Avengers in 1963, the X-Men also in 1963 and the Teen Titans in 1964.
Why the big gap in superhero teams? Blame it on The Seduction of the Innocent!
Thanks to Frederic Wertham; a name that shall live in infamy; and an act of Congress, the superhero comic (which is a native American art form, for gosh sakes!) was all-but-destroyed from 1954-1956.
Even though Superman and Batman had met in 1952, in "The Mightiest Team In The World", for purely economic reasons, they became a legitimate team in 1954 in the World's Finest title.
Not even an act of Congress could force Wonder Woman into the Boy's Club during those Eisenhower 1950s, but her solo title survived this Congressional slaughter which otherwise made superhero titles essentially illegal to publish! The comics industry was devastated.
The debut of the Silver Age Flash in 1956 began the slow return of superheroes from near-extinction and, fitfully, heroes who would eventually be in the Justice League began to team up, like Green Arrow and Aquaman in 1959's "The Underwater Archers", and Superman and Aquaman in 1959's "The Mermaid From Atlantis".
But Wonder Woman didn't benefit from any team-ups until the ensemble Justice League title debuted in 1960!
Not surprisingly, as the Marco Polo of superheroes, the Flash proved a team-up friendly book, frequently hosting Green Lantern, debuting Elongated Man and often guesting Adam Strange.
Atom and Flash even guested outside of their respective titles in 1964s "The Challenge Of The Expanding World".
But Batman emerged as the team-up king, and his popularity in the 1960s led to all-out Batmania in 1966 with his #1 rated TV show starring Adam West and Burt Ward as Robin!
Starting in 1966, Batman teamed with Flash in "The Death Of The Flash", with Green Arrow in 1967s "The Wrath Of The Thunderbird", with Atom in 1968s "So Thunders The Cannoneer", with Wonder Woman in 1968s "In The Coils Of The Copperhead", with Aquaman in 1969s "The Sleepwalker From The Sea", and with Black Canary in 1970s "A Cold Corpse For The Collector".
This was in addition to Batman co-starring with Superman every month in World's Finest and usually appearing in Justice League, as well! Even though Superman had the best-selling solo title, then, Batman was arguably making the most appearances.
Various efforts to have Superman in an additional monthly team-up title have not proven successful. The stories normally go,
"I'm Superman, and you are?
"And what do you do?
"And why are you here?
"Oh, that's nice.
"Now get up, up and away from my face, please!
Wonder Woman's title has never been a comfortable fit for superhero guest stars, primarily because her ancient mythological foundations run contrary to basic superhero cosmology. (For example, the Guardians of the Galaxy from Green Lantern contradicts the Olympian Gods of Wonder Woman. They just do! And the vague kingship of Aquaman in Atlantis conflicts with the uncontested rule of Wonder Woman as princess of the Amazons. It just does! These kinds of kinks have never been smoothed-out in the DCU, which leaves Wonder Woman out of the inner circle and out in the cold.)
Wonder Woman lost her powers from 1968-1973 as Diana Prince: Wonder Woman, during which she resigned from the Justice League and did not rejoin them until 1974 once she regained her Amazon abilities, even though she was with the Justice League title since it debuted in 1960 while Superman and Batman didn't show up for several months, themselves.
Making Wonder Woman integral is the key to any successful JUSTICE LEAGUE movie, something that the comics have been slow to demonstrate! But there is a way to make Wonder Woman indispensable to the JUSTICE LEAGUE!
And, no, it does not involve making Superman her boo!
That way is the Titanomachy! Hola!