Aliens, they're everywhere. We might not be any closer to discovering extra-terrestrial life in real life, but in mass media the invasion has already happened. In film you have all manner of blobs, little brown things with glowy fingers and long necks, cockroaches that love sugary water, horrifying monsters with elongated heads and a preference for exploding out of peoples chests and, of course, walking carpets. TV has numerous examples as well, whether it be men in blue boxes that are bigger on the inside, war-loving guys with creases running down the middle of their faces and pseudo-roman centurions that try to kill rabbits with ray guns. And of course comics are no different. Throughout the around 90 years of comic book publication, there have been many examples of aliens in comics, and in todays list I'm going to rank what I believe to be the top 10.
Now, this list will only include aliens from the comics medium, so no beings from other dimensions or parallel worlds (so no Anti-Monitor, Annihilus, Howard The Duck or Mr Mxyzptlk), any beings which are considered aliens in cannons outside of the comics (so no Asgardians here) and no characters that originated in other medium but have appeared in comics (so no Star Wars, Star Trek or Doctor Who characters here, at least none that really matter because there have been numerous minor characters from those series that have debuted in the comics but never mattered in the grand scheme of things). I'm also not including entire races, so you won't see the Oan's, the Kree or the Skrulls on this list, despite their impact on comics (although individuals that belong to these races may appear). And I'm also not going to include more than one member of any particular race, because then you have half the list taken up by one alien race and the other half divided between another 2-3 which is a bit boring. Oh and no symbiotes. Venom and Carnage are great and yes the suits are alien, but there's still a human in there, so it doesn't count.
Anyway, long enough intro I think. On with the show.
Warning: Opinions ahead. If you don't like it, well, things could be worse, you could be getting attacked by a face-hugger or something.