....and DC had dedicated an 80-Page Giant to that fact.
It was Superman vs. the aliens in 80 Page Giant Magazine #6 of January, 1965....
...and here are the menaces the Man of Steel faced!
Action Comics #234
Superman faces off against Gollo, an alien from the planet Zar who can shape change, and befriends a young boy named Johnny Miles. Gollo finds Johnny, but become separated, as Superman returns the runaway Johnny to his family. While searching for Johnny, Gollo comes to Metropolis and runs into Superman. Superman realizes Gollo is also a young runaway, and reunites the lonely alien with his family, who shows them all of the new shapes he has learned, including that of Superman!
Adventure Comics #274
Superboy brings an alien into Smallville that starts turning its citizens to stone, even a couple that try to leave, for a total of ten people turned to stone. This upsets the law in Smallville who question Superboy, finding out the alien, 6-3kx, was from Zaron, and assigned to find ten criminal alien scientists that nearly destroyed Zaron, who were hiding in Smallville. The ten scientists were also telepathic, being able to read the minds of everyone but Superboy, thus the reason he didn't explain his actions.
Superman's Pal, Jimmy Olsen #43
Jimmy Olsen gets a new pal after the energy of an explosion and Jimmy's signal watch brings an alien from another dimension to Jimmy. The monster appears twice and leaves, then, appears a third time with a deal for the young reporter...to come back to his dimension for a time, after which, the alien will leave Jimmy alone. Jimmy agrees, and once on the alien's planet, finds out the alien wanted him for a horror movie, with Jimmy as the lead monster! After filming, the alien returns Jimmy to Earth.
Action Comics #216
Alien machines attack on Earth, with Superman to stop them. Tracing their path backwards, Superman finds that the machines were constructed by someone who had super powers. While investigating leads on that (mostly other men who Lois Lane thought were Superman), Superman finds a rocket in the forest, with a robot in control of these machines. The robot was made by Jor-El, Superman's father, to make machines to show Kryptonians the harshness of war. Superman destroys the robot and machines to prevent them from menacing the people of Earth.
Action Comics #254
This was only the first two tales of Bizarro (where the monster added a Bizarro Lois), but later tales established a world where many Bizarros lived (not on Earth), making a Bizarro family, so, Bizarro later became an alien from another world (the planet htraE), using Bizarro backward logic!
Adventure Comics #245
With a giant flying centipede being released from the Earth by a volcanic eruption, Superboy had to fight it to keep Smallville safe (even though the creature could manifest Kryptonite as well). Realizing it was a mother looking for its egg, Superboy helped her find her young, and resettled them safely on another planet.
....or a collection of aliens!