There are only two tier one superheroes because Spider-Man and Batman are in a class of their own. Superman is there but not quite and Iron Man is there as long as Downey is involved. They both generate waaaaayy more revenue than anyone else in their respective brands. Wonder Woman is a very solid tier 2 but she can't be compared to those two.
Every Marvel movie that's made a billion stars Downey Jr. so I wonder how well Iron Man will perform following Downey.
Also, one billion is the benchmark only because that's what the Marvel fans or "stans" in this forum wanted it to be. They went on and on about how Spidey and GOTG2 were easy "billy" and neither will get there. They said Thor Ragnorak is an easy billy also so we'll see.
These threads are simply troll jobs on comments that were made