Good one.
I haven't put much thought into, and sadly I soon will, but this is going to be hard to top. Not only is it bang for the buck it's simple and appeals to everyone. The Ultima and Pirate games can be a tad complicated and quirky and not everyone digs those. EVERYONE digs Tetris.

BTW Groovy thread kazmar. :D

The Gold version is superior, the bundle on GOG has 48 MB. If I remember correct, the old version is only a tiny part of that size.

Pirates!
Yes, one of the game i played for months (an all systems).
Ahhh, the treasure hunt...searching the map with only a quarter hint.
I did't like the dance sessions in later versions.
Only the time limit was real bad.

I have gold on floppy disk somewhere and the manual is still on my shelf, I don't think I ever got that high a rank in it... (only low level nobility) I feel that port royal 1 (not 2 because of many annoying changes) is the spiritual sequel many be more so than the dancing one.

Something like a month on the hardest difficulty? Running it in DosBOX requires me to increase the cycles, with the default setting, stearing feels controlling an elephant on rollerblades.

Panzer General (DOS version) could also be a candidate, some search results claim it is ~4MB size.

Darklands !

@The-Business

Than you should see my old PSP....i broke the left controller during a fight ;-)



edit:
i miss Duke Nukem 3D and Syndicate

¬ ¬

Syndicate

Most of the Spiderweb games.

My ex spent 2.5 months strait of her free time playing Roller Coaster Tycoon. I guess she uninstalled it because she texted me yesterday wanting to know what we did to get it working. I don't know what the install size is, but the installer is like 350MB.

When I was younger I burned stupid amounts of time on Master of Orion, and Frontier: Elite2. Frontier would take the award for personal lowest footprint for time played. An entire galaxy of adventure took less than a floppy disc. Not a CD, a 1.44MB floppy

I've managed to fit Planescape, Inquisitor & UnEpic onto an 8GB USB, so maybe look into them

Lords of Midnight, Doomdark's Revenge and Elite for the ZX Spectrum: about 45 kb.