Gotham will bomb because:
BEFORE ALL THE THINGS YOU LIKE ABOUT BATMAN THERE WAS SOMETHING THAT ISNT WHY YOU LIKE BATMAN
Could say the same about Smallville and that show lasted 8 seasons.
Smallville stars Superboy. So it still has what people find appealing about Superman in it. Gotham does not star Batman, and features a young Bruce Wayne. No one will care. More than that, by limiting itself to Gotham, they limit themselves to the chance they could show Bruce Wayne training to be Batman. But that would require being outside of Gotham, and...the show is called Gotham.
The premise behind the series is completely bone headed.
It will bomb. It will likely be a great show due to the staff running it, and I think its quality is the only chance it has at not being a commercial failure.