Depends on the game, if it's an
MMORPG (Massively multiplayer online role-playing game) then it's not unusual for people to play them for years, this is because they're more than just a game, they're an entire community where people make friends, enemies and sometimes even get married (in role play), also these games are usually huge and new content is often regularly added to keep veterans interested, there's also often special events, for instance new special rewards and quests at Christmas when you will find main city hubs all decorated Etc. Some MMORPGs have open world
PvP (player Vs player), others only allow
Co-op (cooperative gameplay), although most still have optional PvP games and tournaments (not everyone enjoys PvP and sometimes they even have different servers that allow or don't allow it in the open world), they also usually have
dungeons where teams of people get together to try and get rare items by defeating difficult bosses, some of the hardest dungeons can take months of practice to fully overcome and each team member needs to for fill a role working together. I for instance played
LOTRO (Lord of The Rings Online) for a couple of years, I was a member of a guild (a group / team of players) that was so serious about the game they used to have regular online meetings via Skype with proper agendas, a formal code of conduct and even a complaints procedure, I became one of the guild officers for a while. It wasn't unusual to meet various long term veterans within the game and even though there's bound to be lots of autistic players, it's not especially a game for autistic people, in fact like in the real world most people are NT.
Some people also get addicted to games like
Call of Duty WW2 and will play them online for a long time, well until the next Call of Duty release which is usually once a year. Online PvP games and also online co-op games that involve playing against or with other people can keep people interested for a ages in the same way as a competitive sport can have very long term interest, like a sport you can improve with practice over a long period of time, there's also a great sense of competition and people can also make friends and rivals Etc. A friend of mine plays virtually nothing but Call of Duty and buys the new version released each year at midnight when there is late night shop opening (there's also new maps released at various points throughout the year), often people rush home to try an get a head start over many rival players and will then play all night until they drop (the longer you play the better you become and you also get upgrades including better equipment and perks while you level up). He's played different versions of the game for quite a few years now and he is NT.
Another type of game people spend a long time playing are games where you can build, these are often survival games like
Rust which again is online similar to an MMORPG, but people create their own content and stories (a
sandbox type game). In these type of games there's an infinite amount of enjoyment as you can build new bases and buildings, plus you can make friends and rivals Etc. Even offline sandbox games can create a fair bit of long term interest, similarly a child could play with
Lego for quite a few years as they can build an infinite number of things.
It's not as common these days with so many online games as I've mentioned above, but sometimes people can play any popular game for a long period of time, even quite simplistic offline games, but there is usually some sense of competition involved, E.g. you are trying to beat other high scores or are involved in online or even very occasionally real life competitions.
I'm not too familiar with Splatoon or Splatoon 2, but I understand there is online co-op gameplay and tournaments so it therefore also has the potential for long term interest, again you can almost think of playing it as a sport. I've taken a quick look online and I see there's also people advertising for guild / team members to play together for instance. It's quite common for people to become addicted to such games and to play them for a long time, even for many NTs, but whether it's healthy or not is an entirely different question. I think it could become an issue if it's played to such an excess that it prevents a child doing important things such as school work and it's not great if they're barely getting any exercise (it's not just children that get addicted to such games however, although some games have higher proportions of younger players).
PS: For anyone thinking about playing LOTRO, it has a much more mature user base on average than many other MMORPGs, but even though it's sold as "free to play" there's lots of restrictions for free players, pay to win elements and I spent quite a few hundred pounds playing over a couple of years to play the game well, and I always could have spent a lot more. It's now quite an old game so the graphics are only average, although there's been numerous expansions and countless updates (the game is absolutely huge).