To beat a dead horse into the ground, I think that the 4 heavenly kings era also denotes a time before corpos really took hold of the market - while they each may have belonged to a company in some sense, I don't think you could attribute that to their success in the same way that you could with the current big names like Pekora, Kuzuha, etc. With the way things are now I feel like you're looking at Holo, Niji, Brave Group, Nanashiinku, VShojo (maybe...) ahead of any individual vtuber.