Gear 2 remains very iconic and continues to age well. You sometimes see the pose referenced at big sporting events.
Kaido's debut hasn't aged as well due to all the agenda/memes/slander, contention, and nitpicking surrounding it. However, I think it's still levels above Katakuri's and Loki's debuts. Xebec's debut was hype, but it lacks the in-chapter buildup that Kaido's had, which was executed very well.
Personally, I'll go with Kaido's.