These are my desert island games. Many of them have ruined entire genres for me because why play a good, new game when I can still play more of these games. To truly play “forever” I need one of:
A staggering amount of content is say 3000+ hours, which would be 8 hours a day for a year. That’s an extremely significant portion of your life on Earth. These aren’t just games with “lots of stuff” like Skyrim, they are mazes specifically designed to trap people on the spectrum.
If I’m really marooned on an island, a game that works as a creative outlet would also keep a game fun even after I’ve exhausted all the scripted content.

Many MMOs would fit here, but OSRS wins because it’s uniquely focused on solo play and even if everyone stopped playing you could still do everything. It takes around 3000 hours just to casually max an ironman and thousands more if you don’t look up all the best strategies on Youtube and the wiki. Maxing is far from the end of the game. Imagine how long it would take to solve every clue scroll alone by yourself.
It’s worth mentioning that this game is designed for people who play 16 hours a day and no one has completed the Collection Log, which tracks which unique drops you’ve received. Think of the most lifelong, dedicated, no life, no job MMO player with all internet resources and the Grand Exchange available to them and realize even they aren’t done with Runescape.
PVP also has a notoriously high skill ceiling and bar to entry. I’m not interested in MMO PVP but if it was the last game on Earth I have nothing but time to learn it.

It’s not the millions of unique platformer levels in SMM2, it’s the sheer novelty and variety of gameplay. There are entire subcommunities dedicated to troll levels, kaizo levels, speedruns, or extreme precision, which are all genres where I’m constantly delighted by unique level design unlike any other video game. The deeper I’ve gotten into Mario Maker, the more certain I am that it’s the best platform game ever made.
Troll levels alone are a unique combination of stand up comedy, stage magic act, and psychological warfare in the form video game level design. It’s one of the most interesting and underappreciated advances in game design and it’s just one tiny thing SMM2 offers a virtually unlimited amount of.
The skill ceiling is as high as it gets too, with many creators grinding for dozens of hours to clear and upload a single diabolical course.
As a huge bonus, learning to design fun levels is a creative outlet and very difficult. This is the only game here where you can make your own games!

Minecraft is certainly a desert island game, as evidenced by its perpetual relevance 15+ years after the initial release. It is just a fun place to design stuff. GTNH is the biggest and most complex Minecraft modpack.
It adds multiple thousands of hours of just progressive technology and automation recipe content, while you progress from stone age recipes through multiple levels of space ages. You go from improving pickaxes to building nuclear reactors component-by-component. There is nothing like this game.
Due to the sandbox creative aspect, plain old vanilla Minecraft would make my list alone, but I’ve seen estimates that GTNH takes 6000-15000 hours to complete. It is genuinely next level for maximalists who want the most stuff in a game. It’s hard to believe it’s free or that it exists at all.

For a sandbox without a years-long guided list of goals, I’d play one of:
Both of these are balanced around not having The End, elytra, villagers, or enchantment tables, which are all some of the worst-designed and least balanced parts of vanilla Minecraft.

I’ve played 1000+ hours co-op without even being halfway done, so Pyanodons Mods easily meet the 3000+ hour benchmark especially with Hard Mode. These mods (and, yes, you should install all of them) add extremely large, complex, realistic, and unbalanced production chains to Factorio. You will have factories that take 7 inputs and output both useful products and byproducts you have to deal with. Each of those 7 production chains is working at a different rate, all with their own complex bottlenecks and problems.
It has a very Runescape feel of setting your own web of goals like “I need A to get B to get C” without being able to conceptualize the entire roadmap for your future progress. There are dozens of ores and materials to mine and process, compared to the small handful of vanilla Factorio. Progress is slow and it’s always worth using your new research, unlike vanilla Factorio where progression is too fast to even require implementing a lot of tech.
After our first 1000 hours with Pyanodons, my wife and I breezed through vanilla Factorio in about 50 hours. We found it simple and boring by comparison as it offers almost zero logistical friction.
To be truly a forever game, use Pyanodons Hard Mode which makes dealing with junk byproducts more difficult and increases logistical complexity (in already perhaps the most logistically complex game of all time).

Diablo II is simply a well-designed, fun game made before video games were intentionally designed to be addictive second jobs. Every aspect of Path of Exile is designed to trap you forever. It has the deepest character customization, the deepest itemization, the deepest crafting, the fastest gameplay, and the most endless endgame optimization. It is the only game I stopped playing out of actual addiction concerns.
The worst part about PoE pulling out all the psychological addiction tricks is that it’s a genuinely fantastic ARPG. If I was addicted to slop like Candy Crush Saga or TikTok, some part of my brain would tell me I’m dumb. Path of Exile hooks you with Diablo-II-but-better-in-every-way which is harder to break free from since my squirrel brain feels like I’m building a nest egg.
Play Solo Self Found so you can’t trade with other players for some truly endless crafting grinds.

Dwarf Fortress is certainly a game that makes other games feel disappointing due to its scale and complexity. I love colony sims and creatively building in 3D space. Its imitators pale in comparison since it’s arguably the most complex game ever made and with 20 years of development behind it, it’s hard to see how other games can catch up. Many, like Rimworld, don’t even offer Z-axis building which alone is a killer feature since it offers so many more creative possibilities than a simple top-down game. Very few 2D colony sims or even survival games offer even meaningful 3D building like this.
Even getting over the initial learning cliff there is endless emergent gameplay to discover by tinkering with its systems. It’s one of the only purely offline, single player games I watch Youtube channels dedicated to.
If DF ever adds an official co-op Fortress Mode, which doesn’t seem likely, this might go from theoretical desert island game to the only game my wife and I ever play again.

Starcraft 2 is the ultimate combination of mechanical skill, reflexes, strategy, metagame, reacting to information, even bluffing. Many other games have huge skill ceilings like Rocket League, DOTA 2, or Counter-strike 2, but none have the complexity or information density that a game of Starcraft can have.
I do believe it’s the highest skill ceiling video game out there, but even if something somehow edges it out, I find the mix of micro and macro management endlessly more interesting than scoring goals or shooting guys. It’s the only video game I’ve ever found interesting enough to follow the esports scene for (besides chess).
I doubt there will ever be a better RTS than Starcraft 2. It is no longer a popular genre and any Starcraft 3 would surely be a mess of modern Activision-Blizzard monetization (even more than SC2 became).

Magic is a weird one because it’s the only desert island game that would have significant ongoing costs. I don’t enjoy constructed play because I feel forced into meta decks and learning matchups that internet experts have already studied. But limited formats like drafts and cube have the variety and complexity I’d love in a “forever game”.
The problem is even in the casual digital form of Magic (Magic Arena), drafts cost around $10 for a couple hours of fun! So yeah, if I had one game to play forever, MTG would technically be on the short list, but it would cost $1000s a year compared to a $30 copy of Dwarf Fortress or Minecraft.
If I’m being specific, I prefer the all business interface of Magic Online to the Hearthstone-esque Magic Arena.

“The ability to play chess is the sign of a gentleman. The ability to play chess well is the sign of a wasted life”
As a chess novice, I understand playing chess well is a lifelong pursuit and beyond shelves of books of theory and strategy, there is an unlimited amount of historical and engine created lines to memorize waiting for you at the top. Freestyle Chess is a variant with randomized starting positions that eliminates the possibility of memorizing 20+ moves of opening theory which sounds more appealing to me, although many more people choose standard chess.
Of all the games here, chess is the most popular.

I’d personally play traditional RPGs with just a notebook and dice, but there are apps such as the Mythic Game Master Emulator or virtual tabletops like Foundry that facilitate playing electronically and I suppose this could be considered a one game forever type deal.
Traditional RPGs have numerous creative outlets of world building, storytelling, and systems design that can certainly keep you busy forever. If I had to pick a single system, I’m a Traveller5 kind of guy, which is an overcomplex, needlessly detailed, and perhaps broken toolbox for generating an entire universe which makes it the perfect game to tinker with forever.
I think most soloists use dozens of supplements to enhance, structure, or randomize their gameplay but if it’s a “one forever” deal, Mythic GME 2nd Edition is the one. This is especially true if you include the years worth of magazines with tons of unique rules and advice for implementing the system in different ways.

I’m leaving video games behind at the end of this list. The electronic version of Kingdom Death: Monster isn’t a forever game, but the hobby of Kingdom Death certainly is. This would be my “lifestyle game” of choice if I had to pick one, an all-encompassing game that takes up all my money and time as it’s an expansive, complex game but also has hundreds of miniatures to paint.
To be honest, I spend 95% of my time with miniatures games painting, so this feels like cheating to call it a forever game.
Warhammer is the classic example of a miniatures lifestyle game, but the solo/co-op nature of KDM makes it more suitable as a desert island game.