I'm partial to the Showa Series
I owned the following on VHS:
King Kong vs. Godzilla
Son of Godzilla
Godzilla vs. Gigan
Godzilla vs. Megalon
Godzilla vs. Mechagodzilla
King Kong Vs Godzilla was my introduction to Godzilla. I also recall renting 1984 on VHS and that was the very last Godzilla film I watched till a few years AFTER High School circa 2001. So I missed out on quite a bit.
^^ That's the exact copy I owned of KK/Godzilla and it was released in 1987, so I was around 6 years old. I upgraded to the Classic Media DVDS a few years ago. Swell releases. They usually include two versions on the disc.