History YMMV / MetalSlug

** Prior to the name reveal in ''Metal Slug Attack'', the Invader King was often referred to by players as the "Invader Queen" or "Venusian Queen". This was because the boss was located in some sort of breeding chamber and was assumed it was the matron of the Invaders.

** The Doctor was usually referred by fans as "Amadeus", stemming on how the Rebel Army and its infantry are sometimes officially called Morden's Army or Morden Soldiers. A full fan nickname "Manfred Amadeus" was also used.

** ''Metal Slug 5'' introduced a ''VideoGame/MegaManClassic''-like slide move. Though it was useful at times, the problem with it was that it was activated by holding down and pressing jump. So most of the time when you wanted to jump and shoot downwards (a common tactic in this series to shoot things underneath you), you would slide instead, and probably die, or at least waste time. Thankfully, it was taken out of future installments. However, once DamnYouMuscleMemory is overcome, the slide is an absolute ''blessing.''

** [[JokeWeapon Stone]] is... well, a stone. That doesn't even explode on impact.

** Allen O'Neil from ''Metal Slug'' and ''Metal Slug 2/X''. Yeah, this guy is extremely hard to defeat if you don't know how to predict his attacks. He can shoot with his Machine Gun and if you try to move to the other side he just tosses a speeding grenade towards you!

** The final mission of ''Metal Slug 3'', which is the longest mission in the entire series. To make things even worse, if you're playing on the Xbox port, you have limited continues, and if you use one, you'll start back all the way from the beginning.

* UnintentionallySympathetic: [[BigBad Morden]] is meant to be kind of a bastard as the leader of the Rebel Army, attempting to TakeOverTheWorld with violence and destruction in a manner that is clearly PuttingOnTheReich, with full liberty of horrible experiments, dangerous weapons, war crimes and even teaming up with ''aliens'' to achieve his goals. Except knowing his origins as a Regular Army commander that lost his wife and daughter to a terrorist bombing that the army could've prevented but originally considered as a prank and [[NeverMyFault blew off the responsibility for it]], gives him a surprisingly earnest FreudianExcuse. Combine that with his VillainDecay as he constantly gets betrayed, screwed over, or made something of a ButtMonkey as the series continues, and some fans started RootingForTheEmpire.

** The Iron Nokana from the first game, while considerably harder than Shoe and Karn, is still easy if you have the Heavy Machine Gun. It can shoot down the missiles, do damage quickly and all you have to worry about is the relatively dense pattern of the regular bolts it has. Once the flamethrower is equipped, you just have to stay away and make it a priority, then stay underneath the boss, which provides you with free POWs, shoot down the incoming missiles and throw grenades for free damage. As long as you pay attention, it's just as easy as it sounds.

** Shoe and Karn from the first game; while they're {{Dual Boss}}es that attacks together, individually they have ''pathetic'' health (for a boss), especially if the player have a Slug at their service. Although they appear together, [[https://static.wikia.nocookie.net/metalslug/images/3/38/Shoe_%26_Karn.png/revision/latest/scale-to-width-down/304?cb=20080705171323 Shoe and Karn each inhabits a single platform]] and are only a threat at their respective positions; so players only need to fight one while avoiding attacks from the other (preferably starting with Karn at the bottom, first). Their forward-facing cannons are only a threat on their respective elevations, while their slow-moving rockets could be dodged by leaping aside; once Karn is defeated, the players can spam their Slug's cannon (or grenades if they don't have a Slug) at Shoe from underneath while dodging its missiles without worrying about the cannons, which is made easier since there's a [[BossArenaIdiocy platform right beneath Shoe]] the players can stand on and lob their attacks.

** The Drill Instructors (Sophia, Margaret, Lilly, Mary, and Cynthia). However, they're hardly qualify to this trope compared to the other darkhorses above, proven by very minimal number of fans and little-to-no fan artworks.

** The Drill Instructors. Their popularity, however, is extremely small compared to the other darkhorses above.

* PolishedPort: The ''Anthology'' compilation that includes six of the seven main games on one disc, running smoothly and allowing infinite retries, while having extra goodies to be unlocked.

* SeasonalRot: ''4'' is generally agreed to be the weakest in the main series. Reasons include recycling ''a lot'' of assets from the previous games (to the point that most bosses are a mishmash of previous bosses in both looks, mechanics and gimmicks), Eri and Tarma being inexplicably [[DemotedToExtra demoted to mission control NPCs]] and [[ReplacementScrappy replaced with newcomers Nadia and Trevor]], and the very few innovations being features that players weren't enthusiastic about (The Metallish Combo System, transition cutscences between missions). It's rather telling that the only thing this game introduced that carried on in future installments was the Two Machineguns.

* UglyCute: The Mars People. They're adorable, in a weird sorta way.

** The Mars People are one of the more popular enemy types (and one that's pretty recognizable even by non fans). A member of their race even had the honor of [[VideoGame/SNKVsCapcomSVCChaos appearing in one of SNK's fighting games]] as a playable character before any of the main cast did.

** The Mars People are one of the more popular enemy types (and one that's pretty recognizable even by non fans).