Cell Saga for the reasons you described. The Abridged version too, which went out of its way to lampshade just how samey and long the Namek Arc was. Earth had far more diverse locales, even if most of them ended up looking like a wasteland before long due to collateral damage.
(Lord) Freiza is certainly terrifying, but there's not much to him past that but sheer cruelty and arrogance. The Androids ran the full range of personalities and powers, and even Cell had to actually earn his transformations though cunning and subterfuge instead of just bringing in another one whenever the heroes thought they had his number. I liked how when he first arrives expecting to flatten everyone, Piccolo straight-up beats him down, forcing a temporary retreat until he's gotten strong enough to snatch his prize at the right moment.
The only major complaint I had was that the new Super Saiyan transformations were underwhelming. The first was a massive shift, but the others added nothing but masses of muscles, and more lightning for Gohan. His in particular should have been more dramatic visually as well as in terms of story power since it was what they were all striving towards for half the arc.
Freiza gave us the Ginyus, but Cell gave us Hercule Satan, champion of the world.
