To be clear, of the ones listed I only care about TOTK and BG3. I'm looking at "megaton games" by a general ascertainment of how relevant they are to the enthusiast gamers, and how much they sell. FFXVI came out and kinda did not great for an FF game so I'll concede there. No idea about Diablo 4, I assume it was middling or "as expected", while TOTK sold 18 million in its first 6 weeks; though I may largely be familiar with that due to being in proximity of Nintendo-related circles.

It really is subjective what measure we're using though. BG3's been amazing in relative terms to what would typically be expected of "DnD RPG" (maybe there's a better term), and developers have been reacting to it far more than they would most other megaton games. TOTK's no slouch on its own, impressing developers over its extremely impressive yet performent physics engine.

https://www.polygon.com/legend-zelda-tears-kingdom/23737921/tears-of-the-kingdom-bridge-physics-game-devs-explain

Anyways, not really interested in arguing my perspective though, since like you said this is extremely subjective, and honestly quite arbitrary.