Random trivia time, the largest NES game ever released was Metal Slader Glory, which was a whopping -- for the time -- 8 megabits. That is, one megabyte. (A round powers-of-ten megabyte, not a computer powers-of-two megabyte, or "mebibyte" as no one would actually call it.)

For context, I reloaded this page and logged it in my browser's developer console. Just showing these comments involved the transfer of 3.06 megabytes (real powers of two ones, at that) or slightly more than triple the size of that entire cartridge. Just to display some kibitzing on the internet.

Most NES games were significantly smaller. The maximum the NES can address within ROM without mapper chips IIRC is 49120 bytes, and many of the initial launch titles, not to mention Super Mario Bros. 1, didn't even fill that whole space.

My man, you just reintroduced "probably". Literally a sentence later. You can check this.

Edit: sorry, that came off a lot harsher than I meant it. Just laughing at "No probably about it... probably"

First result for googling "nointro archive": https://archive.org/details/no-intro-2021

89GB for all known good cartridge game dumps from Atari 2600 to Nintendo DSi.

You can cut that size significantly by using a rom manager program to deduplicate, keeping only the final revision available in a language you speak instead of having every released copy of the game.

Nointro is a group that documents file hashes for good dumps of cartridge games. As in the dump works, it's verified to match across multiple dumping attempts, and it doesn't have any added "intro" crud from whatever group dumped it.

People regularly compile the actual game files matching the nointro group hashes, and toss the whole package up on archive.org.

Disc based games take up a ton more space because unless you start tinkering with the wide variety of compression options, each game is the full size that a disc could handle, even if it physically took up only 1/10 of the space.

Some disc games are nice and don't do anything with the empty space. Some games put random garbage data in empty space, which is hard to detect for compression. Some games put garbage data in the empty space, then check that the garbage data is present at the expected location on the disc as an anti piracy measure.

I think the most compressed that you can go with discs is by using MAME's CHD format, but not every emulator supports reading that format.