This is one of the oldest rivalries in comics and one of the most underestimated IMO. This rivalry started when Superboy met his big brother from Krypton!!

And the rest is history. I'm missing their first fight where silver age was at its peak and neither could even hurt each other!!! But the true rivalry started in LOSH. Their first fight ended in stalemate of course.

But then comes the most widely known fact in this rivalry. Superboy admits that Mon-El is stronger than him.

But nearly twenty issues after, Mon-El and narration say the opposite!!!

I'm searching about the post-crisis comparisons between Superman and Mon-El. I will continue this further soon. Discussion is welcome.