usually they list the levels of the game as separate games too.

there was a company named 'supervision' which created carts like this for various consoles.

their NES carts are not too uncommon.  multi-game carts with a simple menu.  sort of like clone PSPs nowadays, they may say 200-in-1 or whatever, but generally have the same dozen or so games repeated in the list.

not sure if this is a supervision product, but its got the look and the sticker style is right up their with their other bad designs...

Weird mashup games (same game play different sprites) along the originals to fill up space may include:
Sonic-Mario, Super Link Mario, Final Fantasy Mario, Balloon Mario, Bomber Mario, Bubble Dig Dug, Koopa Invaders, Dora Bros, Maria Siss, Mario Mappy, Pikachu Dig Dug ... I'm not even making any of these up, I copied them from my handheld's screen just now.

There are some funny misspellings / misreadings... like Chip 'n Dale Rescue Rangers being called "Chip to Dule 2" in the menu, Seicross becoming "Seacross", Sqoon being "Spoon" etc.

Finally you can get totally different games under recognizable names, like "Pockemon Gold" being some kind of side scroller you've never seen with Pikachu sprites.

Might contain some of your favorite games, like:
Super Mario 1
Super Mario 2
Super Mario 3
Super Mario 4
Super Mario 5
Super Mario 6
Super Mario 7

Or:
Pokemon Beige, Pokemon Teal and Pokemon Salmon!

Also most of the time there are far less unique games on those than advertised, usually by either having a lot of duplicates in the list or also by including a considerable amount of rom hacks that are the same games with different sprites. The same also exist for Game Boy Advance, they usually contain two or three real GBA games and a lot of emulated NES games and rom hacks. In any of those it's usually impossible to save for any game that uses that feature as well.

There are a lot of variations on that theme. Pirated cartridges that hold 10 to 1000 games. Come in all different shapes and colours.

Not originally by Nintendo, as you rightly stated.

The little button on top is to reset the gameboy and choose another game.

I stumbled upon this photo of this weird cart that's way too tall and only says "game" on the top. It's clearly not made by nintendo, does anyone have any information on it?