Perhaps extremely biased considering I am a huge sucker for monster fights but overall this movie was great. I'd give this movie a solid 8.5/10 from a subjective standpoint but objectively it might be lower. The movie had its flaws. Being:
Extremely fast paced: There was so much going in - Godzilla vs Scylla, Godzilla vs Tiamat, Godzilla evolves then suddenly Mothra etc. A lot of explaining was skipped due to the short film time
Action - Action was phenomenal but I think the climax fight could've been longer and with higher stakes. Godzilla and Kong seemed to win quite easily.
Now for the pros:
Action - Action might have been short but the quality was great. Especially the Hollow Earth fight where Mothra came to support Kong and Godzilla. Suko was great too and his character was hilarious. Seeing Godzilla jump from Kong to Kong was amazing too.
Humans - Quite surprising but despite the beginning being a bit boring on the human side, the chemistry was great. And that brings me to perhaps the best human character so far: Trapper. His chemistry with Bernie and sense of humor was great. Jia's story perhaps could've been fleshed out a bit more.
CGI and Choreography - Amazing but there were a few bad CGI scenes here and there.
My favorite moments had to be Kong using Suko as a weapon, The arrival of Godzilla and Kong in HE, and the HE battle. Surface battle seemed a bit too tenseless for me.
Overall, a load of fun and well worth the wait. Give me a more tense climactic battle where Mothra is more involved, and you have my perfect movie. Still well worth the wait!