I think it's most likely that aliens will be friendly.
Consider this, if a species is aggressive, the chance that it will cause itself to become extint by smashing it's planet in a nuclear war etc. is big. So you could say that peaceful, cooperating species will be naturally selected.
Look at us, and how far we've got without smashing our planet. Our view on life and our morals have evolved gradually as our technology became better and we became better at thinking independently. There is still a risk that we will destroy ourselves, but our view on life is still far too good for us to use aliens as slaves to harvest ressources for us. I simply don't think there will be so many aggressive alien species who would do that to us, because most of them would surely have destroyed themselves while they were at our stage.
I voted 5. I would've voted 3, but I don't think they will help us stop our wars. I think they would be friendly though.