Archive Panic: As of this writing, Toho Studios has released a total of thirty-two full-length films starring the Big Guy. If you decided to binge-watch them all at once, it would take you about two days to watch them all (assuming you didn't stop to eat and sleep). If you decided to throw in theAmericanremakes, plus Toho's twenty other Kaiju movies in the Godzillaverse note Rodan, Mothra and its sequels, all of the movies focusing on the Verse's various alien races, etc. the whole marathon would take roughly four days. And let's not even get started on Expanded Universe material, such as comic and video game tie-ins, and the two cartoon series. All of this is without including the multitude of alternate dubs and versions to choose from.
Badass Decay: Well, design wise, compare the fierce Rodan design in the original film to the goofier one in Monster Zero.
King Ghidorah in Godzilla vs Gigan is often seen as this.
Hedorah, arguably tied with Ghidorah as Godzilla's most powerful Showa opponent (the only monster for whom Godzilla's atomic breath was a complete No-Sell) is killed in Godzilla: Final Wars together with Ebirah, after about ten seconds of screen time.
Spacegodzilla. Some view him as cool looking and sinister, while others view him as a bland clone of Godzilla. His generic-sounding name certainly didn't help matters.
There is a slight one between which Showa Mechagodzilla film is better. The more upbeat Godzilla vs. Mechagodzilla with a snazzy tune by Sato that is delighted with playing 70s spy tropes and ape aliens straight or grimmer Terror of Mechagodzilla with brooding music by Ifukube with Godzilla outmatched by two monsters and the aliens look like burn victims now. Both sides agree that both films are a step up in production after the previous two films and of course some like them both for being like day and night.
Big-Lipped Alligator Moment: Some consider the entire film of Godzilla vs Hedorah to be this, peaks with the flying scene. Also the talking scene in Godzilla vs. Gigan.
Godzilla's Revenge, which takes place entirely in a boy's imagination, and has Minilla facing a bully and interacting with the boy (complete with goofy "hyuk-hyuk" voice).
How about the weird hippie couple in GMK, seen just before Godzilla enters Yokohama?
Maguma's entire appearance in Gorath. So much so he was cut from the American dub entirely.
Godzilla's bodyslam in Godzilla VS. Megaguirus is this, too. As is his dropkick in Godzilla VS. Megalon and the time he took to the skies and flew in Godzilla VS. Hedorah is a commonly-cited BLAM to many Godzilla fans.
Fans that often argue toward one another on whether Godzilla's Revenge, Godzilla vs. SpaceGodzilla, the 1998 American remake, or Godzilla: Final Wars is the worst Godzilla movie ever for various reasons. Said reasons include excessive stock footage (Revenge), bad music (Space Godzilla), adaptation rape ('98 and Final Wars), lackluster action (Revenge and Final Wars), ripping off ideas from other movies ('98 and Final Wars), bland story and/or characters (all of them), bad dubbing even worse than usual (Revenge and Space Godzilla), bad updated appearances or the monsters themselves be them new or old (Revenge, '98, and Final Wars).
Also hotly debtated: the best era of Godzilla films. Were the Showa (1955-1975) films fun yet cheesy films or low-budget over-the-top messes? Was the Heisei (1984-1995) era a good throwback to Godzilla's darker roots or were they nothing but wangst and boring "beam war" fights? And, then there's the aforementioned Millennium era. Good luck getting the fans to agree on any one era.
Contested Sequel: Godzilla Final Wars. It's not uncommon to find completely polarizing opinions on this film from many fans to the point that it's mentioned as one of the best entries in the series as much as it is mentioned as one of the worst.
The relatively short fight scenes and overabundance of monsters irritated fans who wanted longer fights and more screen time for their favorite characters. It didn't help that most of them were quickly killed off or beaten by Godzilla.
The emphasis on fighting over story
Arguably, what made Godzilla Final Wars especially polarizing was it's heavy focus on the human characters engaged in kung fu fighting with aliens. Some see it as a nice departure from boring character exposition segments. Others see the emphasis on humans fighting to be distracting and cliched.
Lately, the Millennium series seems to be taking over this role, due to a lack of continuity and a perceived overuse of tropes lifted from popular anime of the time, though there is still some contention within the fandom on this.
Ensemble Dark Horse: With a robust roster of monsters, there are many of these, and nearly every monster is a fan favorite in certain sectors. However, probably the best two examples would be Anguirus, particularly for American fans, and Baragon, particularly for Japanese fans.
Despite only appearing in the first movie (and, even there, having limited screentime) Dr. Daisuke Serizawa is easily the most famous human character in the series.
Megalon. Despite appearing in one movie, he is one of the easiest monsters to play in the Godzilla games. Easy to use in combat and great for beginners no matter which system you're playing.
Gorosaurus and Titanosaurus both have very devoted followings with frequent overlap despite never reappearing outside the Showa Era films.
Despite being scrapped, the Rat/Fish monster Deutalios is popular due to the Toho Kingdom toons.
Though it might seem harmless, don't ever use "Zilla" as an abbreviation for "Godzilla". As plenty of hardcore fans will be happy to explain, "Zilla" was the monster from the 1998 American remake (alternately called "GINO", or "Godzilla In Name Only"), so-called because the fans accused him of taking the "God" out of "Godzilla". If you must refer to the Big Guy by a diminutive nickname, the preferred epithet is "Goji" (short for "Gojira"). Or "Goji-san", if you're the formal type.
Saying Godzilla 'breathes fire' will drive some fans up the wall. They will quickly insist that only the Hannah Barbara Godzilla spat fire. The proper phrase would be atomic breathe/spits thermonuclear energy/radioactive vapor even though plenty of fans think 'breathes fire' rolls off the tongue better and 'thermonuclear breathe' is simply a mouthful.
Fandom Heresy: Criticizing the original film. No matter what your opinion of all the other films are, you're asking for an ass-kicking if you insult the original on any forum.
Love to Hate: Ghidorah, Destoroyah, and Gigan all get this treatment.
Mainstream Obscurity: Everyone has heard of Godzilla, but few people have actually seen many of the movies or know much about them.
Memetic Mutation: In the six decades since the original movie's release, the suffix "-zilla" has entered common English parlance as a tongue-in-cheek way of describing something abnormally large or powerful (e.g. "Bridezilla" or "Momzilla"). Godzilla is iconic enough that people will always know what you mean.
Most Wonderful Sound: Godzilla's trademark roar. It was originally created by coating a leather glove in resin and dragging it down the strings of a double bass.
MST3K Mantra: It's just best not to think too hard about a film series that stars giant radioactive dinosaurs, three-headed cyborg dragons, giant butterflies, giant cyborg monsters from outer space, etc.
Narm Charm: Many of the Showa films, but in terms of characters, Jet Jaguar definitely has so many fans despite being a one-off Ultraman Expy because he's just so laughably silly.
Popularity Polynomial: After 2004, it seems Godzilla all but disappeared from the public eye. But once trailers and footages from the 2014 reboot, fans came back, memes surrounding the movie have started popping up around the internet, and even the general public is becoming interested in the character again.
It's been a slow process, but Zilla (aka American!Godzilla, aka GINO) has been gradually redeemed in the eyes of the fandom. The animated series featuring his more Godzilla-like son (with Zilla as an undead, robotic antagonist) helped, as did his brief appearance in Final Wars, where he received a beating from the original Godzilla. It's in the IDW comic Rulers of Earth however, that Zilla reached his final redemption, taking a huge level in badass and holding his own with the real Godzilla. The comic more or less indicates that Godzilla was the stronger of the two and would have killed Zilla if the fight had continued, but Zilla put up a fantastic fight against big G. The fandom universally acknowledging it as a great moment for both combatants. Zilla also gets some good moments later in the series such as surviving a fight with Destoroyah and being one of the only monsters to evade capture by the alien Tripods and destroyed several of them.
Baby Godzilla and Godzilla Junior showed that Godzilla having a son wasn't a bad idea if executed right.
With the original version of Gojira becoming better known in the States there has been a backlash against King of The Monsters. However numerous historians have pointed out that Godzilla would not be so well known if not for King of The Monsters. Even Raymond Burr as been redeemed somewhat in fan's eyes when it was revealed he refused the comical lines and played his reprisal in The Return of Godzilla with dignity.
Jet Jaguar being able to show off lightning brusier skills and agility against mighty glaciers in various video games and the IDW comic has redeemed it.
Sacred Cow: As noted above, it's widely agreed that the original film is a masterpiece and criticizing it is rare at best. Even people who hate Godzilla movies tend to agree that it's good.
The Scrappy: Minilla isn't well-liked to say the least, largely because of his hideous design and annoying uselessness. Even in-universe Godzilla doesn't seem to like him.
So Bad, It's Good: While this designation applies to much of the franchise, the films in the seventies are particular prone to falling under this sort of designation with plots, monsters, and dialogue that is outlandish even by the regular standards of the series.
Special Effects Failure: Fairly common among many of the movies, although surely the worst are Godzilla's Revenge, Godzilla vs Gigan, and Godzilla vs Megalon, which all include a hefty amount of stock footage.
Surprisingly Improved Sequel: The most commonly cited would be Destroy All Monsters over Godzilla vs the Sea Monster and Son of Godzilla, Terror of Mechagodzilla over all of the other 70's films, with a tiny window of Hedorah over Revenge, and 2001's GMK over Godzilla 2000 and Godzilla vs Megaguirus. Many fans would also say this for War of the Gargantuas, which is a cult favorite over it's much more forgotten predecessor, Frankenstein Conquers the World.
Anticlimax Boss: Legendary Godzilla, the final boss of the single player campaign becomes this if you've hit Burning Godzilla status. Downplayed as his melee attacks are still extremely damaging and if the player isn't careful can easily beat them to death.
Broken Base: The game is rather divisive, with some viewing it negatively especially compared to the Pipeworks Godzilla Trilogy and considering it rather dull and repetitive, while others view it positively and feel comparing it to the fighting games is unfair as it's not really trying to be one so much as a kaiju movie simulator with a large emphasis on the rampage aspect.
Cycle of Hurting: In later levels you've got a time limit to destroy all the reactors while taking damage from the enemy monster, plus the Super-Xs. You have to let them do this to you if want to get to the reactors and destroy them before the time limit expires. Only when the reactors are destroyed, can you think of taking out the enemies.
That One Boss: Even in the demo King Ghidorah is already gaining this rep due to high defenses, melee and range attacks. Which is rather befitting considering his name is KING Ghidorah.
Biollante, due to her long-range vines that she can drive into the ground and then stab Godzilla with in a flurry of rapid-fire jabs, along with her acid sap being very strong and able to push Godzilla back a lot and can even knock him off his feet. It doesn't help that she can also have the Super-X II attacking Godzilla at the same time.