Man of Steel: (2013) $670,145,518
Superman Returns: (2006) $404,231,192
Superman: (1978) $300,478,449
Superman II: (1981) $216,385,706
Superman III: (1983) $80,250,623
This is the top grossing Superman movies, excluding BvS or Justice League (because they are crossover movies, not movies where Superman is the sole attraction). Based on this, Superman making a billion would be all time historic and an absolute game changer (because even BvS and Justice League didn't hit that threshold). Which is why having that as an expectation is crazy, because no Superman movie has ever hit above $670 mill.
If Superman gets to $700 mill or in that range, that is still the highest grossing Superman movie of all time.