When Captain Marvel debuted, he was a pretty standard hero: secret identity, supervillains, all that. He had a mildly interesting character arc, in that he came to Earth as a conqueror but was won over by humanity (like Silver Surfer); he was initially Earth's protector, but the role was eventually expanded to include the entire galaxy (like Green Lantern).
Eventually, writer Roy Thomas and artist Gil Kane gave Marv a quick revamp, switching him from a melange of superhero origins to a pastiche of the other Captain Marvel - the SHAZAM! one. Check out the parallels:
A young boy (Rick Jones, Billy Batson) is lured by a vision (the Kree Supreme Intelligence, the wizard Shazam) to a secret underground location (an abandonned Kree base, the Rock of Eternity) where he gains the ability to change, in a flash of light (clanging the nega bands together, calling forth the lightning), into a red-suited superhero (Captain Marvel, Captain Marvel) with a golden symbol on his chest (a star, a lightning bolt). Eventually, the hero joins the greatest superteam around (the Avengers, the Justice League).
Yeah, I just don't see the similarities.
As a further in-joke, Marv also met Professor Savannah, a nod to Cap's Doctor Sivana. Though Savannah was an ally, not a villain. Also, neither DC nor Marvel have had any luck turning their respective Captains Marvel into commercial successes in the past few decades. Though that one's probably not intentional.
