Aliens that find us will probably be so much more advanced than we are, they'll put us in their zoo, or they'll eat us. There should be a law against contacting intelligent alien life forms.
No. No they wouldn't.
If aliens had the technology to make the interstellar trek to us in any reasonable time frame, then they have moved well beyond the want or need for imprisoning and/or consuming random life they encounter. It's also unlikely that they would want or need Earth for resources, as they would have the technology to easily gather what they need from any number of uninhabited worlds throughout the galaxy. Not only that, but it's also likely that they have moved beyond inconveniences like mortality.
At best, an advanced alien species capable of interstellar travel would find us to be a curiosity. With their technology, wiping out humans, and indeed all life on Earth, would be trivial. They wouldn't need an army or death star like weapon. All they'd need to do is find a nice asteroid an aim it at Earth. Or if they wanted subtle they could engineer a super virus/nano-death-machines and surreptitiously drop it over a major population center.
Or maybe they would just sit back and wait for us to destroy ourselves, since we seem pretty hellbent on doing that. If your practically immortal, then waiting a hundred or a thousand years for a barely conscious species to self-destruct really isn't that big of a deal, and may even provide some level of entertainment.
In short, there really isn't any reason for an advanced alien race to be hostile towards us, intentionally or otherwise.