When I was a kid, Superman was the greatest of all superheroes. There were others with various powers, but Superman was the strongest, the fastest, the most complete. He didn't need gadgets, or scientific mishaps, or magical weapons to perform his heroic feats. His powers were inherent. He was superhuman.
Most fanboys will go to their grave swearing up and down Batman is. He's certainly been shown in the comics to be capable of devising schemes to defeat all of Earth's most powerful superhumans time and time again. But when you look at the evidence, there's a more than strong enough case to be made that Superman has the superior intellect.