On Linux, strace can be used, but you'll need to filter the large amount of output it has. (Using grep to search for "open:" is a good start, for example.)

Standard should be my documents "Game saves" wish it was forced by microsoft or some sort of norm from the early days of windows gaming.

Pretty much because there is no official standard location for save games, and even if there was it wouldn't matter much because there are video games available as old as 1979 (Akalabeth) to current games and any such theoretical standard wouldn't be retroactive, and couldn't be retroactive either since many games no longer have their source code available. Even if it was possible to easily change them, it wouldn't ever happen as developers have no incentive to bother doing this, it would just cost them money for a change that most people don't care about and that has no real major benefit worth the cost it would take to do it.

The only way having a standard location would make any sense at all, is if something was actually enforcing it and forcing developers to use a specific location. That would pretty much mean either the operating system vendor, or the game store itself as a part of its requirements for selling games on its platform having to meet certain standards including where save games and screenshots are stored. Why would a game store or operating system vendor care about this however? It's not like it affects the operating system vendor or store in any way really, so they have no incentive to care either.

Even in the world of open source in Linux we have standard like the FHS (filesystem hierarchy standard) that document which directories in the filesystem should be used for what purposes in order to be "FHS compliant", but that doesn't stop Linux distributions or individual software vendors from installing files randomly wherever and just not caring if they have the "FHS compliant" label or not.

I will agree that having to search down the location of save games, config files, screenshots, character profile data and other data on a per-game basis is frustratingly annoying. Problem is, operating system vendors, game platform vendors, developers and publishers just simply do not care, and the consequences of that are practically zero. I mean, it's not enough people to remotely be statistically relevant are going to boycott buying a game enough to affect sales of the game enough for them to care and change it or something.

There are simply no consequences to the current practice of just doing whatever they randomly feel like, and because of that they just do whatever they randomly feel like.

It's not limited to games either... Look at Discord... it doesn't even install its binaries into the "Program Files" directory, it installs into user account under AppData\Local\Discord\<version-number> which is annoying because I configure a custom profile for Discord in my mouse software and on my Elgato StreamDeck, which automatically switches to the Discord profile when it detects that app has focus, but then a Discord update comes out and changes the directory it is installed into, breaking the autodetection and I have to go set it up again because some developer is mentally insane.

We're doomed! :)

Actually, Akalabeth, and other games of that vintage, typically don't offer a save feature at all; hence, the question as to where the game is saved is moot.

Also, even if we look at games with save features, it still took some years for hard drives to become common; before then, the only place to save a game would be on a floppy disk or even a cassette tape.

I don't bother with the Discord app; I just use the web browser, which means everything is stored in the browser's user profile.

I just wanted to say, another thing that infuriates me is the fact that many save locations are only created once you've made the first save. This means that if, say, I've got some backed up saves that I want to use, then then I will first need to launch the game and start a new playthrough just with the intention of making a single throwaway save file, so that the folder gets created. Pretty dumb, I think.
Any idea as to when they first became ubiquitous?

I am certain Doom and Wolf2D do utilize the saves feature.

I am also sure that Metal Gear (1987) does. However, I've only played the PS3 and PC ports. Might it be different on original hardware?

The NES version of Metal Gear actually uses password saves. When you save your game, you get a password that you are supposed to write down (though, if playing in modern times, you could just take a picture of the screen with your smartphone, or use an emulator). Then, to load the save, you would enter the password, and if it's correct, you would start approximately where you left off. (I say "approximately" because they couldn't save that much of the game state in the password, or it would get too long and annoying to type in, as the password actually encodes the game state.)

Early console games actually didn't have saves as standard, simply because persistent storage was not standard on cartridges. So, different games take different approaches:
* Super Mario Bros. 1-3 don't have any save features at all. (Except Japanese SMB2, where the game would write, to the floppy disk (game is for the Famicom Disk System (FDS) which uses a non-standard floppy disk for storage), how many times the game has been completed. Sonic 1 & 2 also lack saves. I note that many of these games have warp zones or level select codes.
* Zelda 1, I believe, was an FDS game; when the game came out on cartridge (in the US), they added a battery backup, allowing games to be saved onto the cart. Zelda 2 is the same way, and battery backups became more common.
* Metroid was an FDS game, saving onto the disk. The US release is on a cartridge with no battery, and uses password saves. (Worth noting that "JUSTIN BAILEY" is not a special password; it just happens to pass the game's checksum and yield a useful game state.) Castlevania 2 is like this as well.
* Castlevania 1 originally came out for the FDS, with a save feature. For the US release, and for the cartridge re-release in Japan, the save feature was removed.
* Dragon Quest 1 and 2, in their original Japanese versions, used password saves. Overseas versions and all remakes, as well as later games in the series (though 6), all use battery saves.

Also, I believe Atari games, and other pre-crash video game consoles, tended not to have any way to save games. The rare game that did would have had to save to something like a cassette tape (remember those?), and that's just painfully slow.