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.
Some fan have debated as to what Ivan Raidenovitch Raikov's actual fate was, as well as whether recruiting him in Metal Gear Solid: Portable Ops is canon. Heck, there are even some who wonder if Raikov was actually related to Raiden due to their likeness.
Similar to other franchises, the fandom seems to have its divisions. There are the classic purists who state the series went downhill with Metal Gear Solid 4 and that the storyline is getting ridiculous.
A badass soldier with a strange affection and reliance on cardboard boxes is this. Metal Gear Solid 4 upped the ante with the drum barrel which had much of the same functionality plus it could be used to literally barrel over multiple enemies. Peace Walker seems to be taking the crazy awesomeness to even greater heights with a tank-shaped cardboard box (with a working gun turret), an ambulance-shaped box (complete with siren) that can heal people dragged into it, and a "Love Box" that has room for two. There is no implications there at all.
Each one of the Patriots crosses it at one point or another, and that's just with the human founders. Going by the AIs, the AIs probably were already on the other side in a very short time, especially given the fact that not only were they the ones who masterminded the Big Shell Incident as well as the mess that was the war economy, but the Head AI also implied to Raiden that they viewed humanity as nothing more than tools and weapons for them to discard once they no longer serve a use.
Vamp's pointlessly cruel murder of poor Emma Emmerich, Otacon's adorable little sister.
Major Zero. He had Paz Ortega Andrade attempt to get Big Boss to rejoin Cipher (a.k.a. the Patriots). Snake refused, so what did Zero do? He also ordered Paz that, should Big Boss refuse, she frame him and the Militaires Sans Frontières by having her launch a nuke via a hijacked ZEKE at the East Coast, and then pinning them as an extremist cult.
Several plot elements and set pieces used Metal Gear 2 reappear in Metal Gear Solid, with no comment from anybody. Metal Gear Solid 2 returns the favor and cribs off of Metal Gear Solid. This time, the lead character is well aware of this and won't let the player forget as the storyline spirals inexorably towards its Mind ScrewGainax Ending. Part of this has to do with the (then) low profile of Metal Gear 2 and the megahit status of Metal Gear Solid.
This is arguably done purposely across the entire series; There are similarities between Big Boss and Solid Snake's entries into the series that are done to emphasise their similarities and show that Big Boss took the wrong path.
According to the director's commentary, the English localization team apparently did not like EVA due to some parts of her behavior. It doesn't help that the player has to assist her in the most tedious part of Metal Gear Solid 3 and that she appears only in one act in Metal Gear Solid 4 which is considered one of the worst parts of the series.
Raiden's girlfriend, Rose, who's received hatred largely for her relationship drama with Raiden, some of which wasn't written well, as well as a mixture of Die for Our Ship and Stop Helping Me!! feelings. Not to mention the fact that people rarely take kindly to anyone that actually waits until her lover is off at a safe distance - trying very hard not to get killed - before steam-barraging him via digital communication with everything that's bugging her about their relationship. Granted, such an idea could work out with ensuing hilarity. It's mitigated in Metal Gear Solid 4, where her romantic relationship with Raiden is downplayed and she doesn't show up too often, but that doesn't quite count as Rescued from the Scrappy Heap.
While a lot of video games are content to simply let players have fun and let them learn something from the experience if they so choose, this series hammers its players over the head with complex philosophy and hard-hitting truths about the way war works that even most novels shy away from. And it doesn't stop. The repetition may seem a bit like overkill, but it's exactly what makes each game's message so effective, because it will not let you forget. Check out the trope page for more details.
Suspiciously Similar Song: The "Metal Gear Solid Main Theme" is a more heroic-sounding rendition of Georgy Sviridov's classical piece "Winter Road". The theme was first composed for VR Missions by Tappi "TAPPY" Iwase and later given a fresh coat of paint in by Harry Gregson-Williams for Metal Gear Solid 2.
Unconventional Learning Experience: How often do you learn about nuclear weapons, ICBMs, gun mechanics, genetics, psychology, philosophy, Cold War politics, PTSD, etc., all in one video game franchise? Even better: how often do you even become interested in and curious about these concepts?
Villain Sue: Ocelot. Aside from the slight complication of getting his hand sliced off by Gray Fox in Metal Gear Solid, absolutely everything in the many Xanatos Gambits he sets up goes perfectly to plan. By the time he eventually died at the hands of FOXDIE 2.0 in Metal Gear Solid 4, he had achieved everything he set out to do, so he probably wouldn't have cared anyway.
The Boss, particularly in Metal Gear Solid 4. In the preceding game, her politics are presented as something of a moral grey zone, with some good points and some bad. By Metal Gear Solid 4, however, almost every character you meet takes the time to gush over what a wonderful, brilliant person she was, and one character evens states his belief that she was a messiah who was martyred before she could bring forth her vision of a perfect world. Possibly a deconstruction of Villain Sue with the fact that the Boss was actually dead for years by that point, not to mention she never actually betrayed her country, and more of an Alternative Character Interpretation.
When Metal Gear 2 was released, Big Boss had made nuclear threats twice, raised orphans as child soldiers and terrorism which was resulted in the deaths of multiple people. The story in the Metal Gear Solid games has Big Boss being defended by several people. The Patriots brought the idea that Big Boss was fighting in defense.
How Old Snake (and quite a few players) sees the predicaments of the Beauty and the Beast Unit. It's part of the reason why he doesn't really give a crap and why he's annoyed whenever Drebin comes in to explain their origins.
Fortune. Ocelot awesomely calls her out on it, saying that she was "hamming it up as the tragic heroine".
The Woobie: Nine tenths of the major characters in the series. Where do we start?
Nastasha, Otacon, Emma, Meryl, Olga, and Stillman.
Iron Woobie: Snake and Roy Campbell. Big Boss as well, considering how many times he gets blown up.