He was mentioned in the OP, but none other times…I’m gonna give my love for Chewie.
All other aliens nonwithstanding…I think Chewie would win in a fame fight between he (him?) and spock.
I have to agree that Superman, while being the most famous of all aliens by far, is just a ‘superhuman’ from another world. If Luke Skywalker doesn’t count, then I don’t think Superman should.
I feel like prior to the recent Star Wars films, Spock might have won, but I’d bet that since then Yoda has become much more present and famous as an alien than Spock.
Nonsense. Humans were made in His father’s image. 
In TOS Spock put a wool cap over his ears and passed as human in the 1930s. If Superman doesn’t count, then neither does Spock.
Ask the first person you see today what Kryptonite does and they’ll know it is the bane of Superman. Everyone knows Superman is alien.
Superman is significantly different than humans - unlike Luke Skywalker who bleeds, breaths, burns and while might have some magic abilities, could never be anything but human. Superman can fly into space and even fly into the sun. He doesn’t bleed (not even green blood like Spock) nor need to breath nor even worry about burning.
I stick with my original answer. Superman.
Superman is the most famous alien. Most, if not all, of the things that would disqualify him from consideration would also disqualify Spock. After those two, The Doctor would be somewhere on the list but also could pass as a human.
Of the alien individuals that couldn’t pass as human, Yoda and Chewbacca would be high on the list as would Jabba the Hutt.
Take away being an identifiable individual and just go by most famous type of alien in pop culture, I’d probably go for the bog-standard grey. Followed by wrinkled forehead Klingons, the Xenomorphs from the Alien films, Ewoks, Wookies, original series Cybermen and Daleks.
Funny, the first thing that popped into my head was E.T.
My thought exactly.
I think Superman is definitely close and easily wins out if cultural icon status is the issue.
Another vote for E.T. too.
Do Kang and Kodos count? I put them in the top ten.
If someone asked you what species you were, would you say “Earthian”? No, you’d say homo sapiens.
As far as I’m concerned, the jury is still out on whether or not Super Man should be considered homo superus or something completely outside terrestrial binomial nomenclature.
Michael Jackson
Spock has green skin?
I dunno . . . I’m sure a lot of people could tell you they’re from the Simpsons if you showed them a picture, but I doubt a whole ton of people could name them. Only one person besides myself that I can think of in my wide circle of friends and family would know them by name.
What about Frodo
Frodo was from Earth (Middle-earth is Europe in an imaginary historical time), and hobbits are a sub-species of humanity; moreover, the culture in which he lived did not have hte concept of extra-terrestrials.
I think it’s described as greenish early in TOS and in the series bible, I think; it certainly didn’t seem so on screen. (Of course, the color of Kirk’s tunic comes across wrong on screen too.) TNG Romulans are generally greenish in hue, as are many but not all Vulcans of that era. For a fanwank, you can chalk it up to racial differences. Most of the first Vulcans seen by humans were greenish, I’d say, and as a result, it became common for humans to to refer to Vulcans are being green, though there are obviously also Vulcans whose skin tones approximate those of Caucasians and sub-saharan Africans.
Spock is half human.
Spock was green skinned because he had green blood. That is, whatever pigmentation he had as a Vulcan, the blood is supposed to have tinted it green, in the same way your cheeks are pink because of our red blood.
Albert Einstein?
Also, Spock has successfully passed himself off as a human, on Earth, during the 1930’s. The criteria should be that the candidate could not, under any circumstance, be mistaken as human. Just off the top of my head, the distinction should be awarded to something from the Star Wars franchise, ET, or ALF.
How does it come to pass that? Skywalker and Vader are aliens in that they sho ain’t from around here. 