In the last 20 years Batman has had 6 movies, 4 animated series, countless tellings and reimagining in the comics. It is not like either character needs promoting. If you look at the rating not that many people watch Smallville and even if you do, that Clark is nothing like the Superman that most of us know. TAS and Lois and Clark ended around 10 years ago. There is more than enough room to tell a Superman origin story.