Saysumthinfunnymike
VOTE!!!
The problem with this is Superman is arguably the most popular character DC has. Next to Batman.
Captain America and The Avengers aren't top tier.
They have the Disney machine behind them. That is the most important part that you left out of your post. It does not matter who was popular in the comics when you factor in what Disney brings to the table in terms of marketing. You also left out that Robert Downey Jr. is carrying a lot of the MCU on his back. He's worth every penny.
Plus, Man of Steel was an origin flick and many people were turned off by Superman Returns. They made a huge mistake when they tried to continue the Donner era Superman. There were some 40-year old fan boys who loved it but the majority of movie goers do not want to see that anymore. Man of Steel made damn good money considering those factors.
It's comparable to what happened with Spider-Man over at SONY. The first three films made a ridiculous amount of money but Spider-Man 3 turned a lot of people off. Then they decided to do an origin film AGAIN and while I don't think it was terrible, it was a very mixed reaction. Spider-Man franchise should be banking a billion dollars or more every time a film drops. There's no reason it should be doing Winter Soldier or Days of Future Past numbers (i.e. good but not near the potential).