IDK man compared to preventing a gravity enhancing terraforming machine on opposite sides of the planet is no small feat. By comparison laying the hurt on aliens riding scouters who were vulnerable to arrows and bullets seems like a cake walk for someone with Superman's powers.
The aliens in The Avengers were the Keystone Cops of alien invaders. They had a fucking ARMY that had in it's ranks giant flying space serpents and they couldn't even take and hold a few blocks of one city. Seriously, what was their plan? What tactics were being used? None. The whole plan seemed to be "ride in and uh....shoot some stuff up and they'll surrender?"
Some of the Avengers spent a few minutes getting about twenty or so people to safety....the bulk of the time the whole team spent fighting the most incompetent alien invaders put on film. Luckily the government in the MCU was willing to slaughter the whole of New York when faced with a group of idiots on flying scooters and miraculously handed the Avengers with the tool to win the day.
The amount of challenge they would've provided Superman would've been exactly none at all.