I watched Mothra vs Godzilla on Freevee/Amazon Prime, and I liked it a lot more than Godzilla Raids Again, the human story was a lot more interesting this time, and it had lots of fun monster action.
Yeah, MvG is one of the best Showa films. It's basically the same story as the previous film, King Kong vs. Godzilla, but done much better.
It's interesting in retrospect how long it took for Toho to embrace Godzilla as its main kaiju. After the first two films, Godzilla didn't appear for seven years, as Toho tried out other kaiju like Rodan, Varan, and Mothra. Then, when Goji did appear, it was as the villain in films where King Kong and Mothra were respectively the top-billed kaiju. And the next several films teamed Godzilla up with Rodan and/or Mothra, so they were more kaiju ensemble films than "Godzilla films" per se.