On the subject of Godzilla, what's the best one in your opinion? I would like to watch all those movies, only seeing the first one and enjoying that.
Well, in conventional terms, the first one
is the best one. People really like the heavy dramatic element to it; it was so different from every other monster movie at the time, and even now few have even come close to achieving its tone.
Buuuuut... Depending on what you like, there's a few other options.
Shin Godzilla, which just came out in 2016, is pretty fantastic. Some people are bitter about the use of CGI instead of a suit, but in most shots it honestly doesn't look that bad. It's a smart, satirical film, but it's the kind of thing that takes more than one viewing to really 'get', especially if you start to lose track of the subtitles like I do. (Or there's the English dub. Haven't seen it yet, so I dunno if it's good or bad).
Mothra vs. Godzilla (1964, not the 1992 one) is widely regarded as the best of the older films, other than the first. The effects are good by the genre's standards and the human subplot is actually pretty fun.
Ghidorah the Three-Headed Monster is my personal favorite of the 60s films. Great destruction shots, great introduction for what would become one of the most famous 'villain' monsters in the franchise, good human stuff.
If you want ULTRA MEGA CHEESE, I can tentatively recommend Godzilla vs. Megalon, but it's an acquired taste. Most people would say it's just straight-up bad. Vs. Hedorah is kind of in the same boat, but instead of cheese, it's heavy 70s weirdness.
Godzilla vs. Biollante is imo the best of the 80s-90s era. A lot of younger fans like these, but I dunno. The suits look amazing, but they aren't very mobile so most of the fights are just beam wars, and only Godzilla vs. King Ghidorah (1991) has a good human sideplot, imo. Vs. Destroyer (or Destoroyah, depending on how Engrish you like your translations) is...
fine, but most of the middle of it really drags. The ending is super memorable though and that's probably why you'll hear it recommended a lot.
Aaaaand another personal favorite, from the 2000s era, would be -breathes in- Godzilla, Mothra, and King Ghidorah: Giant Monsters All-Out Attack. We usually just call it GMK because that is an awful title. Really great effects and likable human characters. Some people don't like the hero-villain role reversal of Godzilla and Ghidorah, but I think it's neat.
And I'll give a final special shout out to Final Wars, because it's a film that people either love or despise. It's... something. It certainly has the most monsters in it and some very wacky characters. This one's purely a coin flip depending on the person watching it.
I know you asked for a best one and I gave like... ten, but it's hard to pick in a series with over 30 films xU So I hope that's helpful.