Here are some facts on pre-crisis Superman
Super speed
In November 1946, Superman demonstrates the ability to stand invisibly on one spot by oscillating his body so fast that the human eye cannot see him. During this same period, Superman protects bystanders at a navy yard from the effects of a devastating explosion by spinning around the blast area at super-speed. With the speed of light, Superman makes a wall of his revolving body, through which the expanding gases of the explosive cannot penetrate. Then, funneling upward, Superman directs the blast toward the sky.
In August 1947, Superman successfully photographs a series of past events by flying into outer space faster than the speed of light and overtaking the light waves leaving Earth which contain the images of the events he wants to record on film.
Later in 1947, Superman single-handedly constructs an entire underground city in a matter of seconds. (Superman #48) During this same period, Superman uses his command of super-speed to travel through the time barrier into the past*.
*note: Virtually all texts agree that to penetrate the time barrier, Superman must move at a speed exceeding that of light.
Super-Strength
In Spring 1940, when Metropolis is ravaged by a man-made earthquake, Superman supports tottering buildings while terrified occupants dash to safety.
In 1942, he smashes his way through the side of a mountain. By September of the same year, his strength has grown to the point where he can wrench apart a pair of twin mountain peaks with his bare hands.
In 1943, when Superman acts to avert the collapse of a massive undersea cavern, his mighty shoulders bear the weight of thousands of tons of rock and the terrific pressure of the ocean above it. (Action Comics #62, "There'll Always Be a Superman!"😉
1947 brings us the first time that Superman transforms a lump of coal into a glittering diamond. In the words of the text, "Incalculable tons of pressure exerted by the Man of Steel's mighty fist duplicate the work of eons to fuse the opaque coal carbons into the translucent perfection of a glittering diamond!" (Action Comics #115)
By 1949 he has single-handedly created a sun for the Planet Uuz by crashing together its two uninhabited moons and then fueling the resultant atomic blaze with drifting meteors.
But by 1957, Superman is able to hurl an uninhabited planet through space (Superman #110) and in 1958 can produce a small earthquake with a super-clap of his hands.
In March 1965 Superman seizes a spacecraft manned by members of the Superman Revenge Squad and hurls it into a far distant galaxy light-years away from Earth .
Invulnerability
In September 1945, Superman holds open an earthquake fissure with his bare hands until Lois Lane has had a chance to climb to safety. "The most powerful muscles on Earth," notes the text, "withstand the tremendous pressure of thousands of tons of rock!" "If the fissure had closed on me," remarks Superman, "the only damage would have been to the rock!"
In 1946 and 1954, Superman withstands the explosion of a hydrogen bomb (Superman #87) and flies onto an atomic-bomb test site and withstands the successive impact of two atomic bombs. He also withstands the intense heat of the Earth's molten core. (Superman #43)
In 1950, Superman swims underwater thousands of fathoms deep, down to the ocean bed itself, and suffers no ill effects from the crushing water pressure. He withstands the heat at the rim of the sun, estimated at a few billion degrees.
In 1951, Superman can withstand the heat at the core of the sun. (Action Comics #161) By this date, Superman's Herculean body has become immune to all ills and it's impossible for him to get sick.
A text dated April 1965 notes that Superman is invulnerable to drowning, and can remain underwater as long as he wishes.
Super-Breath
In November 1947, when the Toyman attempts to make good his escape astride a rocket-powered hobbyhorse, Superman draws him back to earth with a deep inhalation of breath.
In September 1949, Superman extinguishes a chemical fire by inhaling all the air around it. "The deadly flames are no menace to Superman," notes the text, "who smothers them by momentarily drawing all the air in the room into his own mighty lungs!"
In July 1959, Superman halts a massive tidal wave by freezing it into a solid iceberg with a blast of his super-breath.
In August 1954, far out in space, Superman extinguishes a star with a blast of his super-breath. (Superman #91)
In February 1961, after Mr. Mxyzptlk has loosed a cloud of magic sneezing powder on Metropolis, Superman finds himself forced to give vent to a super-sneeze that literally destroys an entire distant solar system .
A text dated April 1965 notes that Superman is invulnerable to drowning and can remain under-water as long as he wishes.
Are you now convinced? Galactus couldn't stand a chance at the best of the pre-crisis Superman. This Superman had no limits. (He was like a supreme god, able to move faster than light, time travel, destroy stars and solar systems with a single breath, hurls planets, make stars, and survive in the core of stars, etc.)