They'll probably all realize that we're the most amazing things in the entire Universe, then kill themselves out of depression that they could never compare to us. Hell, I have just as much evidence as you guys.
If we see the example of when the "aliens" (the spanish) when they came to Latin America, you know what would happen. And I´m not acting like a crazy childish moron, who takes influence from fiction. When a "superior" civilization encounters a "inferior" one (which would be the case of the human civilization), the "superior" takes measures to take controll and to "educate" the "inferior" one.
Except that the Spanish and Natives were both human. As Romulus said, you're assuming the aliens think and act like we do. There's no guaranteeing they do.