You've certainly left behind one hell of a legacy, and the crowning achievement may just be Mothra vs Godzilla. Many consider this to be one of the very best sequels in the franchise, with some even proposing that it surpasses the original. Depending on my mood, I'd even be inclined to agree. Part of what makes this film work so well is the sense of life and personality with which you were able to imbue your creations, lending the monster battles a surprising amount of emotional depth, which I'll expand upon later.
Your effects work hand-in-hand with Shinichi Sekizawa's script quite nicely, providing some truly great moments of spectacle without overwhelming the likeable characters, enjoyably sleazy villains, and the clever riffs on consumerism (a greedy corporation is seeking to profit from the mysterious appearance of an enormous egg, not caring, of course, that the egg carries the offspring of an entity revered as a god by a South Pacific tribe). Remember what I said about the spirit of innovation kind of dying down in your absence? When the diminutive twin fairies, acting as envoys of Mothra, make an impassioned plea for the safe return of the egg, you actually constructed large scale furniture, carpets, wallpaper--everything to emphasize their small size.
Now, the main event: the clash between Godzilla and Mothra. Upon first glance it seems curiously small-scale compared to many of the series' other rumbles. No major metropolitan areas are flattened as hundreds of extras scream in the foreground. No threat from apocalyptic nuclear devices. What makes it so memorable, as I mentioned earlier, is how well you help us empathize with these monsters. Well, maybe not so much with Godzilla, who is unquestionably the bad guy here; Mothra, on the other hand, is a mother fighting to the very last breath to protect her children, even if she is hopelessly outmatched. Impossible not to be touched by that. The prop you built to bring her to life is superb, and you may find it amusing to know that it would take Toho another 30+ years to live up to the standard you set for the character.
What gives this movie such a timeless feel, and perhaps what I appreciate most about it, is the message that no matter how bleak things may get, how dark, good always triumph over evil. I guess there's really nothing else left to say, other than thanks for everything you've done.
Rest in Peace,