Smallville was a trendsetter for modern superhero TV shows. It went through phases of freak of the week to progressive, connected storytelling. Clark Kent battled villains like Brainiac, Bizzaro, Doomsday and the recurring fear of Lex Luthor finding out his secret. Smallville also acted as a blueprint for a live-action team-up of the Justice League, bringing in Justin Hartley's Green Arrow, Alan Ritchson's Aquaman and other League members. That set the stage for things like the Arrowverse, which took DC TV beyond what anyone could've imagined.
Source：https://www.cbr.com/smallville-better-than-arrowverse-one-reason/
