Current trend in games. It pretty much followed the exact design approach as Hitman: Absolution. Someone somewhere is running round telling game designers that they need to make their games more "cover based shooter" oriented and it'll do wonders for their IP.
The decision to recast the voice of Sam (from Michael Ironside to Eric Johnson), and ostensibly make him look younger (though it was actually the developers needed someone else to portray because of the new motion-capture software, and for what it's worth, Ironside trained Johnson for the role) alienated some fans during the runup to Blacklist's release. Eventually, Ubisoft caved to fans by bringing back Ironside to voice Fisher for a crossover DLC in Ghost Recon Wildlands.
This eased up a bit when Ironside revealed that he was undergoing treatment for cancer when Blacklist was being made.
Can't Un-Hear It: Michael Ironside's voice for Sam Fisher was so beloved that the change to Eric Johnson for Blacklist was heavily complained about.
Although Conviction was generally well-received, some longtime fans of the franchise didn't like the increased emphasis on action over stealth. With Blacklist Ubisoft has attempted to find a happy balance between the action-oriented gameplay of Conviction and the stealth-oriented gameplay of earlier Splinter Cell titles and while it was generally received better than Conviction, quite a few fans of the first 4 games still don't like it as much as them due to the heavier focus on action (Not to the extent of Conviction, though), lack of humor, more Hollywood-esque plot and the change of Sam's voice and personality.
Fanon Discontinuity: The decision to turn Sam's daughter, Sarah, into a Fourth Echelon operative in the Firewall novel and Tom Clancy's Elite Squad doesn't sit well with fans even if one ignores the retcon of Sarah's death. While Sarah is far from The Scrappy, turning her into being like her dad as a preparation for Sam's eventual retirement and Passing the Torch to his daughter is poorly done since there is no explanation or context that Sarah has plans of joining Fourth Echelon (especially after everything that has happened to her in Double Agent and Conviction). or that she is as skillful as Sam.
Friendly Fandoms: With the Metal Gear series, since the basic concept is the same. The games even acknowledge each other with small jokes directed at each other.
Genius Bonus: Some of the Gone Dark missions in Blacklist have really obscure clues as to where to go next.
Harsher in Hindsight: Also a case of Real Life Writes the Plot, Michael Ironside explained the reason he left Splinter Cell wasn't due to his age or a disagreement about the series' direction but the fact he was dying. He had cancer and wasn't certain about his chances. Thankfully, it becomes a Heartwarming in Hindsight that he survived and came back to voice Sam in Ghost Recon Wildlands.
Moral Event Horizon: Both Grim and Lambert may qualify for what they put Sam through by pretending Sarah was dead and arranging for a body to be substituted for her, possibly killing an innocent young woman to do so. While it was ostensibly to protect Sarah and Sam, Lambert didn't hesitate to manipulate Sam's grief to his own advantage. He even admits as much. May be a case of Unintentionally Unsympathetic as it's obvious the developers wanted it to be more of a Shoot the Dog than Kick the Dog once all the facts are out. Quite a few players are never able to look at the two the same way, though.
Narm: The number of times Lambert exclaims "Good Lord!" or other whenever the plot develops, refusing to tell Fisher what he's uncovered (until the next mission's briefing) all starts becoming predictable. It gets to the point that even in the first game during the Chinese Embassy level, when Lambert uses the phrase to express shock at the presence of a high-up Chinese general, Sam repeats it back to him in a feigned shocked tone before dropping back to his normal tone to ask who this general even is.
The GameCube and PS2 versions of the first 3 games were horribly gutted in comparison to the Xbox and PC versions, (for the first game, it is so bad that the Splinter Cell Wiki refers to it as "Version 1" (Xbox and PC) and "Version 2" (Gamecube and Playstation 2)). Because of their weaker hardware, not only is there Loads and Loads of Loading, but there were also many instances where you fight fewer enemies and some levels were reduced in size compared to the Xbox/PC counterpart. In fact, it is not much of a stretch to say that playing the Gamecube/PS2 version and the Xbox/PC versions feel like playing two different games. The first game especially: because the changes to some levels were so severe, the Gamecube and PS2 versions had to insert several additional full-motion video cutscenes to compensate and try to fill in some plot holes. example A big example is the CIA infiltration mission in the first game: the Gamecube and Playstation versions start you off inside the building instead of having to infiltrate it from the outside in a rainy night. Presumably, their weaker hardware couldn't handle the advanced lighting effects of rain and lightning in an outdoor nighttime setting. As stated earlier, a very flimsy Hand Wave is given where they had to insert a cutscene with Sam using a fake ID to get in. Another big example is in the final mission of Pandora Tomorrow: you must kill 9 terrorists in the Xbox and PC versions but only 6 in the Gamecube and Playstation versions.
For the first game, on the PS2 side to make up for this, an extra level was added between the Kalinatek and Chinese Embassy missions where Sam investigates a Russian nuclear power plant. This is actually a plot-critical level because it reveals where General Feirong obtained the nuclear material for his missiles. But because the power plant mission is only available in the PS2 version, players of the Xbox, PC, and Gamecube versions will have no idea what Lambert is talking about when in the second Chinese Embassy mission he starts freaking out about some "missing Americium-239" the player was never told about before that moment.
The first two games eventually became this on PC. They were directly ported from the original Xbox version, and as such were optimised for a number of contemporary Nvidia and ATI cards that supported a form of shadow mapping called "shadow buffers", first supported on the GeForce 3 and the NV2A GPU used on the console. While it did work on most hardware at the time, later graphics cards, driver versions and DirectX APIs broke functionality for said buffers, causing spotlights and other projected shadows to no longer work. As lighting and shadows are key elements of the gameplay, playing the original Splinter Cell and Pandora Tomorrow would be an ugly and unpleasant ordeal with a lot of trial-and-error. Fortunately, the first game does have a fallback mode for systems incapable of rendering shadow buffers, but Pandora Tomorrow lacks it, which may account for why it is the only Splinter Cell game unavailable through Digital Distribution. However, there is now a fan made fix for both of those games.
The "three alarms and game over" mechanic. Nobody complained when Chaos Theory replaced it with alarms making mooks get progressively more well-armoured and alert instead.
Although they might just be a vocal minority, some Splinter Cell fans absolutely hate the Mark and Execute feature added in Conviction, feeling that it makes the game too easy even on the highest difficulty.
Novels:
Harsher in Hindsight: The Shadows terrorist organization, meant to be more dangerous than Al-Qaeda and tech-savvier while even more fanatical, is actually a fairly decent approximation of ISIL.
Money, Dear Boy: The reason Raymond Benson wrote the first two novels.
Periphery Demographic: The novels have a decent-sized fanbase who have never even heard of the video games.
proves, this ain't the first time Michael Ironside played a hard-boiled man named Sam being concerned about his laundry.