I like Byrne’s run a lot, and he did a lot to develop the characters and do interesting things with them that enriched them hugely.
But I’m not sure anyone can compete with the relentless imaginative outburst of the initial Lee/Kirby run. The concepts they threw out are still being mined today - Doom, Inhumans, Black Panther, the Kree and the Skrulls, the Watcher, the Silver Surfer, Galactus, the Negative Zone, Annihilus, even reintroducing Everett’s Namor to the new Marvel Universe. I don’t think many (any?) runs on any superhero book can touch it for raw creativity.
Byrne was arguably able to go to more sophisticated places though, partly due to the way comics had changed in the intervening years. The Sue Storm pregnancy/miscarriage storyline is the one that really sticks in my mind from his run as hitting hard.