I admit my descriptions are rather idiosyncratic as I deliberately exclude high complexity games such as Space Opera. They certainly are old school, part of the "realism" movement of that early period but they aren't my focus. This also rules out GURPS (whose 1st installment Man to Man came out in 1985) and Champions (which came out in 1981) which I see as Archaic Modern, in that these games still are played widely today with surprisingly little rules drift
An old school game is a table top roleplaying game with light to medium rules complexity released in or before 1985 and is either out of print (save via retro-clone) or whose rules have changed considerably since that period to the point where early editions lack compatibility with the modern game of the same name (FREX Dungeons and Dragons)
My list includes
1- OD&D (and its retro-clone Swords and Wizardy)
2-AD&D (and OSRIC)
3-B/X/C/M/I (and Labyrinth Lord )
4-Cyclopedia D&D qualifies as well, though released in 1991 is contains essentially only material from games that qualify) and Dark Dungeons does as well since its mainly a darned good retro-clone of Cyclopedia
5-Adventures Dark and Deep as its thematically a lot more old school than new
6- The Fantasy Trip (and its retro-clones)
7- Most of the TSR books (Gangbusters, Boot Hill,Star Frontiers)
8 -Basic Roleplaying /Call of Cthulhu et all. These games are on the high end of the complexity line but they changed little enough that I had no trouble playing Mongoose RQ when I hadn't played a BRP based game in a couple of decades.
9 - Tunnels and Trolls and its cousin Mercenaries Spies and Private Eyes
10- Dragon Warriors just makes the cut (1st book out in 1985)
11- Fighting Fantasy
12 Traveller. Another game on the high end of the complexity limit but that is certainly old school too.
Honorable mentions go to Castles and Crusades, for trying to bridge the Old/New Gap, AD&D 2e a system I dearly love and in whose early days , was certainly quite old school and GURPS, who probably deserves to make the list but just doesn't pass the "feel" test.
I'd be interested in any y'all think deserve the list that I overlooked ...
The Return of Planescape? - Curious. There is a brief note on this 'countdown' at Enworld.
13 hours ago