This is the lockdown generation, so it's also the way to socialize with real world friends.
So that's my answer. Candy Crush.
You mean free game bundled with your OS?
Nokia: Snake
Windows: "3D Pinball for Windows – Space Cadet" or Solitare
TI83: If it was used, hopefully phoenix.
If you want a good EV Nova clone https://endless-sky.github.io/
Roller coaster tycoon: https://github.com/OpenRCT2/OpenRCT2
www.addictinggames.com
More like game that was tolerated or more likely encouraged to be played during school time. In my 4th-6th grade levels, we'd regularly (once or twice a month) go to computer lab, where we'd have an hour maybe? to fiddle around with the computers. Sometimes there was a specific program we were working on, sometimes it was free choice. In 2nd-6th grade we also had a computer or two in the classroom as one possible free choice activity (or in 2nd grade, I'd always be finishing my work early and asking for 'special permission to play with the computer'), but the software selection was all at least mildly educational. Oregon Trail and Number/Word Munchers were a staple. If nothing else, everyone in my class learned not to go on a trip with 5 people all named the same thing, because it's confusing when someone gets dysentery.