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.
Its sequels have mitigated this somewhat. After Resident Evil 5 and Resident Evil 6, it's hard not to look back on 4 as the most subtle and haunting of the "new age" Resident Evil games.
What's better, the Red9 or Blacktail? Arguments over this rage to this very day.
All the Escort Mission sections. Some wish they were gone entirely, others think they actually weren't that bad, and that Ashley does a pretty good job of staying out of your way most of the time.
Big Lipped Alligator Moment: There's a giant clockwork mechanical statue of Salazar in one of the castle chapters. Never explained or mentioned ever again. We can buy that Salazar has a big enough ego to build a statue of himself, but why build a giant clockwork statue that chases after people?? His ego is just that big.
The guy that bursts out of the furnace on fire could qualify as this too. What the hell WAS he doing in there?
Critical Research Failure: When they were called out on the use of the Spexico trope, the developers defended themselves by saying the game doesn't take place in Spain, but in Central Europe. Looks like nobody told them Spain is the only country in the whole continent where Spanish is spoken and the "pesetas" were Spain's currency before the Euro...
Damsel Scrappy: Ashley Graham. You'll hear "LEON HAAALLLP" so much that you're bound to want to kill her yourself by the end of the game.
Ramon Salazar to an extent as well. He certainly delights in causing trouble for Leon and Ashley and steals every scene that he's in.
That dog you save from the trap at the beginning of the game. The Video Game Caring Potential is nice, but what cements him into the hearts of fans everywhere is when he repays the favor by helping you kill your first El Gigante. Capcom had made another game called Haunting Ground where an identical dog called Hewie spends most of the game as the protagonist's loyal companion.
Epileptic Trees: There's a lot of WMGs regarding the identity of the Merchant. Many about Hunnigan as well.
Even Better Sequel: The Resident Evil games were always well liked, but this game is considered the apex of the entire series. It's sitting at 96/100 on Metacritic and is considered the game of the year for 2005. It's been released on multiple platforms and holds the Guinness Book of World Records for best selling survival horror game. It did so well and is so liked that every main entry Resident Evil game since 4 follows it's template and tropes. Not to mention how it's credited for bringing the Third-Person Shooter viewpoint into new prominence and inspired a lot of other games, such as Dead Space for one.
The suit of armor that you can equip Ashley with makes her completely invulnerable, even from enemies that try to kidnap her.
What makes this even worse is that you can switch costumes on your first Professional Mode playthrough... Meaning that you can play through the entirety of Professional Mode without having to worry about Ashley's safety.
The P.R.L. 412 can kill Mendez, the Garradors, Armaduras, Verdugo, U-3, Krauser and even Saddler in no more than two stun flashes. Utilizing both of these features a player could complete everything in the game using nothing more than the base handgun, one box of ammo, three grenades and a handful of healing items. Post-PlayStation 2 versions made it even more game-breaking by giving it faster charging speed and its charged shot will decimate everything in front of Leon.
Goddamned Bats: The Novistadors are not well-liked among the Resident Evil community. At least they kidnap Ashley so you don't have to look after her...
Also, Crossbow Ganados. They are annoying as sin, especially when you can't tell where they are. They also have excellent accuracy on Professional mode, and will do more damage than you'll be pleased with.
Plagas count too. Specifically, the second and, especially, third forms. The second type is only dangerous on Professional due to it potentially biting your fucking head off, but the third appears to exist specifically to piss off players accustomed to using flash grenades or shotguns to kill plagas.
Ashley was able to suplex goons via a bug in the original GameCube version after stunning certain enemies by busting a door open in their faces!
During one of the mine levels, there's a part where you have to fight two El Gigantes in a small room. It's possible to make one fall in the lava that's under the floor, which kills it after a minute. In the GameCube version, if you left the room and then came back, there would be money on top of the lava pit that you could pick up (the reward for killing El Gigante). This was fixed in later versions.
Also in the GameCube version, during the Salazar fight, there was a spot near where the tentacles come out of the walls on either side where Salazar would not attack you. The tentacles would try to hit you if they were out, but otherwise you had complete impunity to whale on Salazar. Again, this was fixed in later versions.
Screw the guy who blasts through the undead scourge and penetrates the deepest levels of the sewers to save the president's daughter. We want to know about the guy who's so badass he beat us there and set up an item shop and shooting gallery.
Ashley's alternate costume, a suit of armor that renders her invulnerable, makes a clanking noise every time she walks. It's only negative aspect of the armor, but it's frequent enough to make you want to mute your TV.
Moral Event Horizon: Osmund Saddler transforming peaceful villagers into bloodthirsty savages to do his bidding, as the credits would suggest.
Most Wonderful Sound: The soft clarinet music you hear in some saving rooms is very relaxing, especially when you just went through a hellish survival sequence. This is pretty much tells you "Don't worry, it's safe here."
Older Than They Think: Quite a few new fans of the series don't seem to realize what the "4" in the game's title actually denotes.
Paranoia Fuel: The fact that some decapitated Ganados will keep walking forward for a couple seconds before keeling over might be an unintentional quirk of the game, but it actually ends up adding a lot of tension, as it leaves you guessing for those few seconds whether a Plagas will burst out of their neck or not (while likely still having to deal with other enemies.)
Polished Port: The Wii edition has everything the original PC version claimed it was going to have, and on top of being perfectly stable, it even has God-tier controls. The HD Edition version, released on PlayStation 3 and Xbox 360, has higher native resolution, added shadows and colored lighting in many locations. The PC port of the HD release, dubbed "Ultimate HD Edition", is kind of meh as far as graphical options go compared to the likes of Devil May Cry 4, is playable at high resolutions, has an added hi-res texture pack, has controls comparable to the Wii version, and can run at 60 frames per second. This is opposed to...
Porting Disaster: The original PC port, which claimed it has the graphical quality of the GameCube with all of the PlayStation 2 version's content. It was a buggy pile of crap with visuals that are MUCH uglier and colorless than the PlayStation version that needed to be patched (and modded) to hell and back to even be playable. What's also ironic is that the PC port PC of RE4 was handled by SourceNext, the very same company behind an improved (and unfortunately Japan-only) PC port of Resident Evil 2.
Rescued from the Scrappy Heap: The knife. Code: Veronica pulled it partway out by making it hit hard enough to be useful, if you knew how to use it properly. 4 gave it the extra push by making it less situational, quicker and more simple to use, and not take up inventory space, among other perks.
That One Boss: The battle against Salazar can be challenging even in Easy. It doesn't help that Salazar can instantly kill Leon with one move, though he can only do so if he's standing too close to him.
The first fight against Krauser involves several quick time events that if not pressed correctly Leon will die. The game will change the prom every time the player loses so this is not about memorizing but training reflexes.
That One Level: The very first level, where all you have is the basic pistol, a knife, and maybe a couple of grenades. After facing about six enemies in groups of at most two, you come to the village where you can end up with about a dozen villagers, two with chainsaws, coming after you.
The "Ball Room" in late game. There's little space to maneuver, Elite Mooks are coming at you from every direction, who have the highest Plagas spawning chance in the game and will constantly get reinforcements until you've taken down a substantial amount of them, and you have to protect Ashley during the whole process. Prepare to hear "LEEEEEEEOOOON!! HAAAAAALP!!" a lot.
The water level in Mercenaries, it is the only place in the game that has SUPER Dr. Salvador. It also doesn't help that this is one of the few levels in Mercenaries where there is little to nothing in the way of good camping spots.
Mike the helicopter pilot. How many times in this series can you say you have a chain gun and missile launcher-toting helicopter coming to your aid, and doing a damn good job at that? It's nothing short of a travesty that he and Leon weren't able to stop by that bar he mentioned.
Uncanny Valley: Ganadoes seem human at a distance, but as you get closer their red eyes and odd movements push them into the valley.