I agree.  The developers used the same character model as Superman but the color scheme was intended to invoke Captain Marvel.  Remember that DC had licensed the rights to Captain Marvel back in the 70s and I would assume this was an extension of that license.  To be frank, I had never heard of Captain Marvel before playing this game but my friends who had IMMEDIATELY recognized him and thought it was one of the coolest things about the game.  In fact, if it wasn't for this game I wouldn't even know who Captain Marvel is or what the word "Shazam" is referencing