Fridge Brilliance: Scientists not believing Mafune's story of a dinosaur in Japan seems silly at first, considering how kaiju attacks are taken as everyday occurrences in the '70s films, until you remember that his initial discovery of Titanosaurus took place fifteen years prior. People would still often react with "A giant monster? Surely you're joking!" well into the 1960s, especially considering that fifteen years would've made it 1960 - Major events like Mothra and King Kong vs. Godzilla hadn't even happened yet.
That, and considering Japan had already suffered the wrath of two Godzillas, two Rodans, Anguirus, and Varan, perhaps the scientific community were Properly Paranoid, and were in denial about the possibility of such events happening again.
True Art Is Angsty: The film has received alot of popularity with the darker and more serious Japanese version becoming available in the United States, but the film is still full of plot holes. Sure, it's a good movie, but being dark doesn't necessarily make it an underappreciated masterpiece.
Vindicated by History: It has its flaws, as do all Godzilla movies to various levels. This film had the lowest box office attendance but is well liked by many fans today, mainly due to Titanosaurus and the large amount of Scenery Gorn.