Not really no
First of all, he is not a fan fiction insert, so if he did apply, it would be under the label "canon sue". Not nearly as catchy, I know, but still.
Secondly, both Mary Sues and Canon Sues are mainly characterized by an unreasonable level of competence at everything they put their hand to, and being the center of the spotlight for everything they're involved in. Superman may seem to fit this at first, but him being extremely competent at what he does makes sense within the lore of the fiction he is in. Thanks to what he is, the term omnipotence is not all that inappropriate. He is also not always in the spotlight. Now, the lore giving him these abilities happens to be utter bunk, but that is a different gripe.
First of all, he is not a fan fiction insert, so if he did apply, it would be under the label "canon sue". Not nearly as catchy, I know, but still.
Secondly, both Mary Sues and Canon Sues are mainly characterized by an unreasonable level of competence at everything they put their hand to, and being the center of the spotlight for everything they're involved in. Superman may seem to fit this at first, but him being extremely competent at what he does makes sense within the lore of the fiction he is in. Thanks to what he is, the term omnipotence is not all that inappropriate. He is also not always in the spotlight. Now, the lore giving him these abilities happens to be utter bunk, but that is a different gripe.