Actually that is partly how life is theorized to have formed on the earth (by means of meteor impact) from "nothing". Amino acids forming in the early days were smashed into by meteors which (through proven scientific means) created peptides. This later morphed into life as we know it in the primordial soup.
Slightly different from your method but very similar in that life was formed by means of impacts of space rocks. Amino acids are pretty easy for nature to create, and there's lots of rocks floating around out there to smash into planets. So if this process i mentioned happened here, there's every possibility that it could happen anywhere else in the universe (within reason.. not on a star etc
) And that life would, in the basics, be similar to other life on our planet since it was formed through similar means with similar chemical compounds.
While it wouldn't explain why greys look so much like us it would help to show that life out there could be extremely common.
The simple fact is, we don't know at all if other life was around in our solar system on other planets cuz we just haven't gotten a good look yet. There very well may have ben life on mars 1million+ years ago before the water was locked away in the soil and poles or lost to space. Water oceans under the ice of europa could be swarming with life but we wont know till we go. The surface of titan could have life forms completely different from ours *shrugs* just because the recent probe didnt spot any on the way down doesn't mean it isnt there (it was only alive on the surface for like 30mins-a couple hours tops, and it didnt move around to look, it just sat in it's ditch). There may be water volcanos on titan (water instead of lava) which makes you wonder what could be in that slush.
Even here on earth there's microbes that gather enough energy to reproduce only 1 time in thousands of years. Plants and animals that live at the mouth of volcanic vents on the ocean floor in the scalding/boiling water. Who's to say it can't be on another planet?