Say what you will about Arrow, but it certainly did not fail this network.  Premiering on The CW on October 10, 2012, the show ran for 8 seasons and spawned what would become known as the Arrowverse, which includes fellow DC-based programs The Flash, Supergirl, Legends Of Tomorrow, and Batwoman.  As of today, the Arrowverse has been responsible for 25 seasons of programming on The CW.

The abbreviated 8th, and final, season was a precursor to the Crisis on Infinite Earths crossover, which not only brought together the heroes from all of the Arrowverse series, but changed the footing underneath them moving forward.  Whatever the actors move on to next, they will always be able to say that, after years of floundering, they gave an identity to The CW.