Say a Reticulan (yes a Grey) comes to our planet, with his bags...or whatever they use to cary things, and sits at a hotel and goes
"Man your oceans are sweet" and one of use (humans) could show him around the particular place, and explain plants to the being, and explain our weather patterns to him/her. Not that we will all be scientists in the future, but we will know basic things like we do now (I hope) Imagine explaining what a fly is to a being from a planet that doesn't have a corresponding life form for it.
"What is this creature?"
"Oh that's a fly, annoying little [censored]ers"
"What do they do?"
"Decomposers, they eat dead bodies, or rotting things"
"That is quite efficient"
To be honest, I think if that future were to happen, Humans would develop a sense of Planetism (like Nationalism, but for a whole planet) And though it would be scary to think about now, if all of earth became one government, and there were no American's, or Mexicans..etc, just Earthlings?
The aliens (I hate using that word) would not always be humanoid to be sure! Some could probably have a more insect like shape, or maybe even similar to the Turians from Mass Effect universe?
What do you think? Could this be a possibility? Would you want it to happen?