(but totally enjoyable at the time)
1) Argos catalogue game. Close your eyes and open a random page. Everything on the page costs a penny. What will you choose? (Tried playing the game as an adult but it doesn't work because you just think about the actual monetary value)
2) Sudden Holiday! Quick - we're going on holiday to [place] in ten minutes! You can only take one carrier bag of things! Don't forget the suncream!
3) X many Y cars before Z. Sure, a not-at-all sad classic when played on the motorway. But pretty much a winner when played in the age-old context of sitting on the porch (summer) or windowsill (winter, extra sad points) waiting for your dad to come pick you up. Extra extra points by the time you get to "the sixth blue car after the next red van (he's probably broken down...)".
4) Not quite as sad, but trying your best (and failing) to play role-playing games based on TV shows you haven't seen because you didn't have cable.
5) Imaginary tea. Usually begun on the third consecutive night of jacket potato and beans. Every individual bean is a different food! Sausages, chocolate, green beans, pineapple, so much variety so much yum! You have to take it in turns with sibling(s) to eat each bean and can't use a food they've already chosen.
(Only-child games don't count, you're entire childhood existence was sad)