Oh boy, if you didn't like Part 1, you're really gonna hate Part 2.
I didn't think it was terrible, but it is underwhelming. It's essentially the same story as Part 1, just told on a slightly larger scale - this time with a larger, more powerful Godzilla, a Mechagodzilla city, nanometal, etc. But there's no traditional Mechagodzilla (Mothra is hinted at, Ghidorah named dropped at the very end) and the characters resort to the same plan that destroyed the smaller Godzilla in Part 1, albeit with cooler toys. There is some focus on the ulterior motives of the Black Hole inspired aliens, but it's not enough to feel like a satisfying standalone experience, something I felt Part 1 was able to do for the most part.
Lack of cooperation among the various races (human and alien) seems to be a theme, leading to the film's downer of an ending - another thing it has in common with Part 1. They're all back to square one again, and Godzilla is seemingly more powerful than ever.
Whether you liked Part 1 or not, a common feeling was that with all the world building out of way, Part 2 would push things forward and deliver the goods, but I don't feel that's the case here. Part 3 REALLY needs to pay off a lot of the build up in 1 and 2 (Mothra, Ghidorah, Mechagodzilla, the ultimate goals of the aliens, etc.) for this trilogy to be worthwhile.
Exterminate all rational thought.