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.
Anti-Climax Boss: You will have a bunch of weapons that are super effective against the final boss and if you train the right characters to use them, you can kill him fairly quickly.
Also, Valter goes down way too easily and without much ado for someone who's been a major threat for about three quarters of the game.
Each floor of the bonus dungeons has a promoted "boss" monster. In Lagdou Ruins though, most of the enemies will be promoted, and the boss is the only one who doesn't scale — so it's often the weakest enemy on the field by far and has about 2/3 the stats of the surrounding flunkies.
Eirika. Some people think she's fine for being a Naïve Newcomer and goes through realistic Character Development to become a strong Lady of War by the end, given that her upbringing was solely focused on diplomacy and she made a personal effort to learn swordplay before the game even started. Others think that the game script is sexist for handing her the Distress Ball a few too many times while her brother gets Cutscene Power to the Max. And whether or not handing Lyon the Sacred Stone was stupid, or understandable given their long friendship and the Demon King's silver tongue.
Whether or not Innes or Seth is a good romantic partner is a point of some contention. Some people find one or both of them sexist, feeling that their protective attitudes border on the possessive, some think it makes sense due to their personalities/upbringings/political positions/etc. and like their supports fine... some fans just get annoyed with all the arguing over her potential romantic partner since that's not even what Eirika is concerned about for most of the game.
Broken Base: When the Nintendo 3DS rerelease came around, there was some minor consternation over whether The Sacred Stones was really the best GBA representative for the franchise. Most of the people who were complaining wished for Blazing Sword instead.
The game itself among the Fire Emblem fandom; detractors say it was too easy and short compared to other games, fans love it for its worldbuilding and the return of various mechanics from Gaiden.
Canon Sue: As far as Fire Emblem is concerned, Ephraim is the pinnacle of this trope. He is an unrealistically brilliant Ace who is amazing at nearly everything he does, and his one weak subject (anything to do with books) borders on being an Informed Attribute - he’s such an incredible tactician that you wouldn’t know he’s Book Dumb unless you paid attention to flashbacks. You want to know how great of a tactician he is? He can storm entire castles with a mere three allies like nobody’s business, and he escapes the clutches of Valter, who almost curbstomped Seth at the beginning of the game and can outrun Ephraim’s entire group. He abuses cutscene power to live through the plot, gets away with his Leeroy Jenkins tendencies when he clearly should not be able to power through certain situations, and is unrealistically perfect in every way conceivable. And of course, everyone idolizes him. The only ones who don’t are either villains (and even then, Valter is clearly… excited to fight such a Worthy Opponent) or they’re Innes (who is all but stated to be jealous of how unrealistically perfect Ephraim is). Lyon’s jealousy of Ephraim’s sheer perfection actually caused him the psychological damage that drove him into his position, as revealed in Ephraim’s route. No, seriously. If this guy is not a Canon Sue, then there is not one to be found in the entire Fire Emblem series.
Small aversion with Caellach. Despite the fact that he's an obviously evil person, he's actually the least evil and is just a Machiavellian man of ruthless ambition. Compare with Riev and Valter (who practice demon worship and are Axe Crazy, respectively).
Demonic Spiders: The Baels are actual demonic spiders, but they have obnoxiously high enough physical attack and defense to fall under the spirit of the trope as well.
Double Standard: Eirika is reviled and hated by fans for needing to be rescued twice. Innes needs to be rescued twice as well, and in one of these times it's Eirika who bails him out... but no one picks on him.
Gheb was just some random Gonk that takes little to no difficulty to kill, but the fandom sees him as a Memetic Molester who stabs others to death with his penis.
Lute is also definitely one of the more popular mages among the whole of FE-dom, thanks to her odd habits, her endearing braggadocio, and the related fact that she can back that boasting up with results. (Her married endings being adorable are also a plus.)
"Funny Aneurysm" Moment: In-universe - In a flashback, Ephraim states his father "will likely outlive us all." Year and a half later...
Hilarious in Hindsight: Likewise in the same conversation, Ephraim states he rather be "traveling the land as a mercenary", and Erikia chides him for it. During the game, Erika is pretending to be a mercenary leader.
The S-class weapons deal ridiculous damage to monsters. The game compensates for this by throwing a shitton of monsters at you in the final levels.
Bishops have a class skill that makes them deal triple damage to monsters. The majority of the enemies you face are monsters, so bishops are very powerful indeed. Plus, they're your party's main healers, so their utility does not just extend to monster levels.
Ho Yay: There's a fair bit in the game, most prominently in the mixture of admiration and rivalry between Ephraim and Lyon and Eirika's Romantic Two-Girl Friendship with both L'Arachel and Tana.
It's Easy, so It Sucks: As a relatively easy game in an otherwise Nintendo Hard series, it draws this reaction from some fans. Then again, some point out that it's still harder than your average game, so it kind of depends on what context you're using.
At least until the Brutal Bonus Level, which is suddenly able to reduce level-capped characters to fine paste.
Love to Hate: Valter and Riev are just to hilariously and unrepetently evil.
And then there's Joshua, Handsome Lech who's too busy losing all his money even if he rigs a game to be malicious, or cheating in order to keep from killing a nun, and also he's the long-lost prince of Jehanna. Those Jehannans, huh?
Memetic Molester: Valter. Admittedly, it's not that much of a stretch as he's far too happy to track the twins down. Also, Gheb, who isn't exactly a stretch either, given his dialogue with Tana.
Memetic Badass: Gheb is invincible, and the "Gheb" one fights as a boss is actually his loser twin brother Gleb. If the actual Gheb were used, the game would be impossible.
Moe : Amelia, Myrrh (less in the "super cutesy and adorable moeblob" sense and more in the "sweet child who goes through lots of shit" one).
Moral Event Horizon: Novala from stage 8 gleefully traps several Renais citizens in the mountains to be killed by giant spiders during the fight after they fail to work as hostages for Eirika's surrender. When Eirika is horrified by this display of pointless cruelty, Novala just laughs and says that this is war; any atrocity is fair game as long as you win.
Everything Valter does. Riev's approval of Valter's savagery puts him over the line too.
One-Scene Wonder: Morva makes a badass entrance at the beginning of his chapter and looks like he may be the Eleventh Hour Ranger. Instead, he gets killed and subsequently turned into a dracozombie.
To elaborate, Caellach has a close-combat axe... AND a hand-axe. He hits like a damn truck in either one of them, and not even the Lords will survive at Lvl. 20. You have two options: hope that one of your units survive his attacks, or take the easy path by summoning mooks to slowly waste the uses for his hand-axe to THEN bombard him with magic from far away. Also, his in-story rival, Joshua, is a myrmidon/swordmaster, and Caellach comes equipped with a Hoplon Guard, this game's equivalent of the Iron Rune.
Carlyle on Eirika's route may be even more annoying. He's a Swordmaster, so that automatically means high speed, hit and avoid. Avoid which is boosted by the throne he's on. Good luck hitting him, and there's no way you're doubling without powerlevelling Joshua or Colm. Both of whom will probably go down in two to three hits. And he has a crit bonus. And a 2-range sword (though he cannot critical at range because of his weapon).
Tier-Induced Scrappy: While loved as a plot character, Knoll is HATED as a playable one for his poor stats and the general weakness of dark magic in this game. Summoners in general are considered the worst overall class, too, though careful use of their summons can prove surprisingly effective.
A majority of the Bonus Characters who have lackluster stats and growths, as well as limited potential.
The Woobie: Knoll, to the point that he actually expresses relief in his death quote. Amelia, who is also a Plucky Girl and refuses to let it get her down. Myrrh, who is already a Shrinking Violet.
The country Grado in general has its forces decimated, 85% of its high ranking levels killed off, the entire royal family killed, and then undergoes a massive earthquake after the epilogue.
What an Idiot: When Fado gave his children bracelets that act as a twin key to Renais' Sacred Stone, he ordered Seth to not tell them what the bracelets were until "the time was right." Seth, who is usually smart and a bit Genre Savvy, inexplicably refuses to give Eirika a detailed explanation of its true nature—this while her brother is missing, possibly dead or captured, in enemy territory with the second and they themselves are on the run. He only tells her that losing it puts the whole continent at risk from the Demon King after Novala demands it in exchange for hostages and she—not having any idea that it's more than a very important but not magical or world-risking royal artifact—decides that it's not worth people dying over. Admittedly, he didn't know that Grado knew, but after the bracelet had already been stolen once and necessitated a desperate detour, he really should have given her the whole story.
This has become worse ever since Fire Emblem Awakening has her in the Bride class, despite still being a fighter on top of a staff user. Even more baseless because you can download a version of Eirika that is still a 100% Swordswoman (more exactly a myrmidon, which makes sense since her Lord class is VERY similar to it), so the above "Bride Eirika" is an optional event that can be taken or not.
Woolseyism: Ismaire's original name was Ishmael. Since that's a male name, it got approximated to the more feminine sounding Ismaire.