These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Contested Sequel: Every Final Fantasy game somehow manages to become more controversial than the last one.
Crack Is Cheaper: All thirteen games, for Sony consoles, were bundled together as part of the franchise's 25th anniversary. Said bundle's price? $446.
Critical Dissonance: The entire series. Critics almost universally give Final Fantasy games high scores. Fans on the other hand are a heavily fragmented Broken Base. Name any game in the series and, though the proportions will vary, you will find people who hate it, those who love it, and those who don't feel strongly either way.
Growing the Beard: It is generally agreed that the series has done this, but there is no absolute consensus to when this happened, being the subject of massive Flame Wars. General consensus is it happened somewhere from IV to VII. Each game in that span, in their own ways, radically improved upon the gameplay, plot and/or characters compared to what came before.
The franchise may also be on the way toward pulling this offtwice; XII was divisive, XIII was polarizing and XIV was the biggest franchise disaster since Spirits Within. But the Realm Reborn version of XIV is drawing in a hell of a lot of positive attention, Bravely Default is basically tallied with the franchise and is wonderful, XV is the game a number of people (including Nomura) have wanted to make since the Nineties (and the resulting trailer quality is leading to a lot of hype), and while Lightning Returns is still polarizing for various aspects, it so far has a fairly positive reception based on trailers and gameplay footage, and in Japan, Type-0 was real damn good. Now if only we'd get that last one overseas...
Also, people can't seem to get straight who does what in the production. People often blamed for the direction of a game or the story are actually the character designers. (Granted, this is not assisted by a fairly prominent example of a character designer moving up to a director's position where he did have more control over game and story direction, or getting top billing in games where he's still merely the character designer.)
My Real Daddy: Some fans will tell you the series began to lose its way once Hironobu Sakaguchi resigned from Squaresoft, and its subsequent merger with Enix from 2001-2003. Following this came the Compilation, the slew of remakes and ports of earlier titles to handhelds and smartphones, and the troubled development of XII and XIII, all of which lend some grain of truth to the opinion.
Granted, this was only really obvious in the Japanese promotional art. The English promo art used in Nintendo Power and the likes was... different.
Percentage-based damage. The Gravity spell family—which first appeared in Final Fantasy V—is the most famous example of this: Gravity takes 50% of the enemy's HP, no matter how much HP he has. However this first appeared all the way back in Final Fantasy II with the Blood Sword, which always took a certain percentage of the enemy's HP, no matter how large it was.
Scapegoat Creator: As mentioned above, some people tend to blame the wrong people for the direction of the games. note Nomura is (usually) merely the artist, and not always even the head artist.
The Scrappy: There's usually at least one character per game that nobody wants in their party, no matter how good they are.
Sometimes entire games are considered Scrappies in certain parts of the fandom, which is a small part of the reason behind the Broken Base.
Sequelitis: Much like the beard-growing above, a majority of the fanbase is of the opinion that the series is suffering from this now (or is just now clawing its way out of such), and just like the beard example, nobody can quite agree or pin down where the rot first set in, or if it's even been a consistent malaise. A lot of oldschool NES/SNES-era fans say VII, a fairly significant number these days say VIII, some point the finger at X, some at X-2, people who dislike the MMO entries pulling resources away accuse XI... you get the idea.
About the only thing largely agreed on is that XIII and the original version of XIV are/were the most significant expressions of the problem. Final Fantasy All The Bravest also gets a ton of this sort of flak.
Silent Majority: These games are best-sellers, but you would not know this by looking around the internet, though. Before examples were removed, the Final Fantasy fandom was listed as an example of the fans who still buy the games and enjoy them, but don't feel the need to scream about it on the internet.
True Art Is Incomprehensible: Pick any game from the Final Fantasy franchise. Good luck trying to follow its plot. Even the original, with the most lightweight plot of all, manages to be confusing with what it has.