If you loved Terror of Mechagodzilla, try The Mysterians
A bridge between a film you've already seen and one most people haven't. The Mysterians has roughly 4.0× fewer votes than Terror of Mechagodzilla — it's a deeper cut, not a mainstream recommendation. Here's what they share, and what the second one does that the first one doesn't.
What they share
Both films are directed by Ishirō Honda, and they sit in Action / Drama / Science Fiction territory. If that's the register that drew you to Terror of Mechagodzilla, the second film will land in a comparable space — through a different lens.
What The Mysterians is
Japanese village. Autumn cicadas. A vanished people. Aliens arrive, seeking land and wives after vaporizing a swatch of Earth. A colossal robot erupts, incinerating what's left. Humanity faces a choice: annihilation or subjugation. Honda's paranoid, post-Hiroshima nightmare gets a vivid, widescreen treatment.

