While Frieza was soundly defeated twice over the course of Dragon Ball Z, the fan-favorite villain returned for a surprisingly prominent role in the follow-up anime series Dragon Ball Super. Initially appearing in his usual antagonistic ways seeking revenge against Goku and the Z Fighters, Frieza was later recruited by Goku in a shocking move to help represent the Universe 7 team of fighters during Super's climactic storyline, "The Tournament of Power." While Frieza played a pivotal role in securing Universe 7's final victory, one of the big questions is why Goku chose to complete his team with Goku instead of the previous Z villain Cell.
Created by the fiendish Doctor Gero, Cell was a synthesis of robotics and genetic experimentation, with Gero splicing the genes of different fighters into his ultimate creation to seek revenge on both Goku and the androids that had betrayed and killed him. Absorbing the life force of hundreds to augment his power, Cell could also regenerate from even the most grievous injuries as long as his core was still intact. And possessing the DNA of many of the Z Fighters, Cell could mimic all of their most powerful special moves and techniques, including the Spirit Bomb.
After achieving his perfect form by absorbing Androids 17 and 18, Cell easily bested both Vegeta and Future Trunks before fighting against Goku in the Cell Games. Cell not only was the first opponent that Goku ever gave up against but one of the few to cause his death by forcing Goku to heroically sacrifice his own life rather than allow Cell to destroy the Earth. And self-destruction only made Cell considerably more powerful, with the villain's Saiyan DNA allowing him to grow stronger after recovering from each significant injury, letting him nearly overpower Gohan even when the young Saiyan was powered up to Super Saiyan 2.
The problem is, Cell never escaped Hell like Frieza to grow even stronger. Early in Super, Frieza's army used the Dragon Balls to resurrect their fallen master, who quickly began to rigorously train himself to grow exponentially stronger than he had before being killed by Future Trunks. As such, even though Cell was far stronger than Frieza had been in his initial appearance—even containing cells from Frieza from the tyrant's brief visit to Earth—Frieza has grown far stronger, able to transform into a new Golden form and stand toe-to-toe against Goku while the latter was Super Saiyan Blue.
Despite his memorable appearances menacing the Z Fighters and helping usher in the Super Saiyan 2 transformation as a coming-of-age antagonist for Gohan, Cell never really played an active role beyond his appearance in Z. The non-canonical Dragon Ball GT had Cell and Frieza form an impromptu alliance to trap Goku in Hell, but the Saiyan had far surpassed both of his opponents who similarly weren't allowed to grow stronger in the afterlife. This would be the last major appearance of Cell in any of the anime series, easily bested by a Goku that had been reverted to the body of a child.
With Frieza's power level now arguably comparable to Goku and Vegeta prior to the former unlocking the Ultra Instinct transformation, the galactic tyrant was an easy choice for Goku to make over Cell. True to his word, Frieza was fully resurrected for his role in helping Universe 7 triumph in the Tournament of Power and has already menaced the Z Fighters once again back in the land of the living. Cell, however, remains firmly languishing in Hell, just as strong as he was when he was destroyed by Gohan. That said, as evidenced by Frieza, the possibility for his return even more powerful than ever before remains for the long-running anime franchise.