Awesome thread, and good points about other animals just having different intelligence!
I agree that aliens capable of creating the technology to come over here to greet us would probably empathise with our technological skills. They would no doubt see us in a similar way as we see neanderthals.
Also, it's our actions that could attract visitors- the artificial radiation patterns we send out into space etc, in which case they'd be coming over to see what we specifically were up to. I'd be surprised if slugs or bees or whales were doing stuff that could attract far away visitors.
Maybe they didn't need spaceships, but just swam through space or something. Maybe they wouldn't even be as intelligent, and would just swim over here, gobble up all our forests, and swim off to find the next nutritious planet.
We are assuming here that the aliens are pack animals, in which case they would probably be more interested with social species like us than loner species. If a loner alien came over here, he probably wouldn't be a threat or much of a source of knowledge, so not the kind of aliens that WE'RE interested in, unless he was somehow intelligent all on his own (is that even possible?) or shat dark matter as a defence mechanism or ate planets etc.
The only aliens we're interested in are ones that come over and are like us in some way- we wouldn't think much of a shoal of space-termites or something travelling around trying to find a new home, and we'd probably just wipe them out unless they wiped us out with their dark matter excretion defence mechanisms or nasty disease or whatever! Yes, maybe we've already been visited but they were so small that a little boy stepped on their landing craft!
Aliens who found the scale or gravity or climate of our planet inhospitable might not visit us at all, but just have a look from afar.
Maybe they would just 'think' their way here in which case they'd probably be most interested with the most thoughtful species (is this us? The bonobo are pretty thoughtful but without communication here on earth every individual has to be Descartes, Newton and Einstein all in one lifetime to rival us). Or yes maybe we've already met them in hyperspace.
I think that if they were intelligent, they would be most interested in us, because we obviously now shape this planet more than any other animal, so that would get them interested. Sheep may eat the vegetation off the ground, but we have built the hedges around their fields, for example. I think it would be obvious that we were the dominant species to an intelligent visitor. Of course, they may not approve of our dominance, but that would just influence the way in which they were interested in us. Nature isn't pretty, you don't have to be human to do awful things. Black widows eat their husbands. Mice eat their young. Ivy grows up trees and suffocates them parasitically. Trees compete with each other for rootspace and the strong suppress and kill the weak.
Maybe they would be like many of us or worse and would enslave or kill us, or be vengeful and cull us or render us extinct so the bonobo can think in peace. Or maybe they wouldn't be space-Nazis, but would still kill those of us who they didn't judge worthy of life and let the nice ones live on, maybe even forever (just like the Abrahimic god allegedly promises to do!). Or maybe they'd think we were awful creatures and would just leave us alone like how we leave lower forms of life to bicker amongst themselves in the wild.
I'd like to think that when they arrived, they'd ask to speak to the earth's diplomats, so all the world leaders would get on video screens from inside their bunkers. But the aliens would say "Who are these jokers, bring us the Nexus!" And Obama would say "What's the Nexus?" and everyone would scurry around until some C I A creep would say "What about that website we've been monitoring?". We'd all get busted in dawn raids and think we're going to jail but then they'd bring us to the aliens who would act like our buddies and all the straits would eat their hats. And they'd lock up Cheney and all the other assholes and we'd all eat spacecakes and live happily ever after. Haha!
I have no idea whether a form of life more intelligent than us would enslave us, kill us, befriend us, command us like parents, or ignore us. But I do think that any alien that had more in common with other animal forms of life would be interesting to scientists but not many other people (after the initial shock of meeting the herd of space-locusts and the following cull of the cosmic herd). I'm in no doubt that if aliens visited and didn't immediately show that they were more armed and dangerous than us, our militaries would immediately just wipe them out while they were still in space if they could, for fear of catching something or being tricked into submission, then just pick up a few survivors and cadavers to poke around with.
Everything I write is fictional roleplay. Obviously! End tribal genocide: www.survival-international.org Quick petitions for meaningful change: www.avaaz.org/en/
End prohibition: www.leap.cc www.tdpf.org.uk And "Feeling Good" by David D.Burns MD is a very useful book.