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.
Arc Fatigue: Despite only being four episodes, their Civilization V: Brave New World series is three hours long. That, combined with the hosts' general ignorance of the game, makes it hard for some fans to sit through it all.
The show was revealed on the exact same day JonTron left Game Grumps, thus causing the base to shatter even further. RubberRoss confirmed that the timing of Steam Train's beginning was terrible and the show had nothing to do with Jon's departure.
One of the most unpopular aspects of the original show is the duo's general inability to Read the Freaking Manual and instead whine about not understanding the controls. This carried over to Steam Train, making certain episodes very frustrating to watch for people familiar with what is being played. The They Bleed Pixels series, for instance, has Arin and Ross complain at the inclusion of a forced tutorial, and then again when they fail to perform certain tasks because they didn't pay proper attention.
The Eryi's Action series. Some don't like Ross's uncharacteristic grumpiness, some don't like Arin's attitude, some think they should play a "better" Platform Hell game, and others think it's fine and hilarious as usual.
After the 1st Year Anniversary, the format changed slightly, specifically changing the cast much more frequently, even to the point of not having Ross on some episodes. The more vocal commentators on Youtube complain loudly about the new direction, from the games that are played (they're trying a bunch of new games) to the people on the show.
Making dicks in video games when available is generally seen as very boring, low-brow humor. However, the creatures created in the Spore Creature Creator are generally seen as hilarious due to Ross's high enthusiasm for them and the fact that he tends to come up with a new creative design each episode, each one usually more horrifying than the last.
The end of the episode for the Graveyard. The old woman in the game dies, and shortly after the group decides to ask Barry to put links to various other things, including 360 no-scope and cat videos, around the woman's body.
The first episode of Hotline Miami was derided by a huge portion of the Game Grumps fandom for a variety of different reasons, ranging from the over-abundance of silly voices to a total lack of skill with the game despite playing the tutorial to resentful feelings toward Dan for being on both shows on the channel. Just a day later, the first episode of Castle Crashers debuted to a much better, largely positive, although still average reception. Many fans have pointed out that their chemistry is developing in much the same way that Jon and Arin's did in the first few episodes of its parent show. "Castle Crashers 2" is the first episode to receive a generally very positive reception, with many noting that, while they still didn't find it quite as funny as Game Grumps, they still found it very funny and entertaining.
Steam Rolled — special episodes focusing on four-player multiplayer games where Barry and Suzy participate in addition to Arin, Dan and Ross — was a well-received variation on the usual format, and helped cement the show's place within the channel. And it even caused Barry to become an Ensemble Darkhorse.
Ho Yay: Barry and Ross' recent Sims4 playthrough takes this to whole new levels with Sim!Arin and Sim!Danny.
However, a huge part of the problem was that Steam Train's format is completely unsuited toward playing that game. Just about the entire point of Presentable Liberty was the sense of isolation and helplessness the game builds in the player, which doesn't come across so well when you spend the entire game joking around with your husband/wife, who's sitting right next to you. It doesn't help that Arin, probably the worst person in the entire Steam Train cast to be playing a game like this, was at the controls; case and point, he spent the entire time focusing on the deliberately shoddy minigames, at times outright ignoring the incoming letters to play them.
Memetic Mutation: "God dammit, Ross" has caught on as a joke both inside and outside the show; it is often used to reinforce Ross's Butt Monkey status. By the time of The Stanley Parable, it has become such a big part of the show that the demo version they were sent includes the actual narrator saying the line as part of specially recorded audio.
Nausea Fuel: In the thumbnails for their I Am Bread play-through, the slice of bread becomes more green and moldy with each episode.
Nightmare Fuel: Doubling as Paranoia Fuel, during a Skyrim episode, Barry's omniscience is discussed. He reacts by superimposing an eye and some really creepy music onto the screen as Ross and Danny continue commentating, oblivious.
Their creatures in Spore. Giant penises running around mauling everything in their path.
Replacement Scrappy: The South Park: The Stick of Truth series, for replacing the unexpectedly popular Go! Go! Nippon! series. The fact that the game is considered bad for Let's Plays and Ross continually spoiling jokes, later plot points, and a complete inability to upgrade or gather friends doesn't help.
Arin has received a lot of flack for effectively replacing Danny as the main co-host in 2014, January to May only having 17 episodes out of 150+ where Arin doesn't appear. Danny came back a little starting in June, but shortly afterwards he left Steam Train to have time to work on his music, and Arin went back to becoming the default cohost with these complaints becoming more common.
Rescued Fromthe Scrappy Heap: Go! Go! Nippon! had a cold start due to the first episode being reminsc of Hot Line Miami with Arin and Ross reading text with funny voices. Not even a minute into the second episode Arin suggests changing gears and aside from the finale the funny voices are abandoned and Arin tells stories about Japan, Ross jokes about Splatta-Doo Specials and some near nudity here and there. The series ended up being one of the more memorable ones.
The Duke Nukem II playthrough. Nintendo Hard + Arin and Ross's usual level of competence = A very boring, repetitive, and frustrating time for both the fans and Arin and Ross.
The Dark Souls 2 playthrough. It would be one thing if they were just playing poorly, but Ross is admittedly drunk and seems to be intentionally playing badly and overly hamming it up. It was so bad that Ross, in the comments of the first video in the subreddit, pre-emptively apologized for how badly they were playing in this series. However, some believe that the apology makes it worse, as Ross apologized before the series showed them playing badly. This suggests that they knew that the series was terrible, but decided to upload it anyway for whatever reason.
So Bad, It's Good: Their opinion of the ''Barbie: Life In The Dreamhouse" game, with Ross getting very involved in the minigames.
So Okay, It's Average: What fans initially thought of Steam Train during its early days, with fans still very upset at the sudden changes. This ends up being Subverted however, as fans grew more attached to Ross and Danny and accept them as much as they did for Game Grumps.
Special Effects Failure: One of the biggest complaints about "Hotline Miami" was that the recording equipment, for whatever reason, was apparently causing the game to run at half speed.
Surprise Creepy: Offspring Fling alters the "Arin the Bandit" intro to accommodate the fact that Danny isn't playing. In this one, Arin kills Danny, and growls "Say it" at Ross, who lets out a terrified "Choo choo."
They Just Didn't Care: Trials Fusion is one of those Steam games that has the product key appear in the bottom right, in case the game needs you to input it after launching. Instead of getting rid of that pop-up before they started recording (or even during recording), they imposed a Wendy's ad on top of it and didn't get rid of it until the second episode. The second episode also had them abandoning the campaign levels and going to the custom levels. However, since they had unlocked no content beforehand, the majority of custom levels were unplayable and the video was 70% cycling through menus.
Uncanny Valley: "Ellen Degeneres" in their playthrough of Dark Souls 2.
Win Back the Crowd: "Castle Crashers #1" received a great reception in comparison to "Hotline Miami #1", to the point where "Castle Crashers #2-4" preceded "Space Quest IV #1", and where "Space Quest IV #4" and "Castle Crashers #7" preceded "Hotline Miami #2".