Either character is as strong as they are written to be.
Hulk is a more well-liked and popular character now, and has been in a successful string of movies. Movies featuring the Hulk have grossed what, 8 billion dollars worldwide? Superman fizzled out, the actor wisely bailed, there is nothing slated to star Superman for years on out. He's washed up.
His comic book son, the last interesting aspect of his solo comic book, was aged up and thrown in amongst the space-transvestites of the 30th century.
In animation and vidya gaems, Superman is only interesting as a twisted, evil parody of himself, which really says a lot.
His franchise is more badly damaged than Star Wars.