I thought this might be an interesting fun exercise ... especially where an expectation may be proved wrong one day.

I'll start off with a couple of easy ones, though I am sure you could probably add the whole Valve Collection.

Half-Life
Half-Life 2

Reasoning - Owned by Valve who own/run Steam.

Please give your reasoning for each game you mention.

This topic could also be a guide of what not to bother waiting for here.

Decent ones

FULL LIST (alphanumeric)

Age of Empires 1-2
Blood Omen: Legacy of Kain
Discworld
Dune
Dune games
Geoff Crammond's Grand Prix 4
Grand Prix Legends
Half-Life
Half-Life 2
Heretic 2
Indian Jones Desktop Adventures
Mario
Mechwarrior
NASCAR Racing 2003 Season
No One Lives Forever 1-2
Outrun 2006
Portal 1-2
Richard Burns Rally
Skyrim
The Lord Of the Rings (EA) games
Zelda

Any old sports or racing game with licensing.

For example, any EA Sports games (noncurrent year).

There's Descent, if you're not too fussy about the spelling.

A whole lot of older / classic racing sim milestones such as Grand Prix Legends, NASCAR Racing 2003 Season, Richard Burns Rally and Geoff Crammond's Grand Prix 4. Obvious reason: expired licenses / difficulty to acquire licensing again.

RBR was sold until only a few years ago, so maybe that one can still be obtained. And don't forget netKar Pro

Zelda, Mario and all the other Nintendo franchises i would assume.

The orignal, not "reforged" Warcraft 3 - because that will likely never be sold anywhere ever again (except for used physical copies).

world of warcraft (or any other MMO)
Diablo 3
Diablo 4 (when released)
Rocket Arena
Among Us
Apex Legends
The Settlers (new games - same name - not yet released)

and many, many more

Would it truly be Diablo 3 without Error 37?

DayZ Standalone.

you are so clever with your memes

- Portal 1-2 (for the same reason as Half Life's).
- Dune (because apparently the rights holder hates the games or something?)
- No One Lives Forever 1-2 (because the rights holders can't find their own ***holes even with both hands and a map...)
- Skyrim. (There's going to be at least another 12 re-releases. Maybe after Skyrim 2050 - The Remastered Legendary Definitive Enhanced Ultra Ultra HD Special VR Edition...)
- Age of Empires 1-2. (Same reason as Skyrim. When you can release exactly the same game "new" every 3 years, it'll never be an old game / drop in price...)
- Outrun 2006 (and most other racing games with licensed cars). (When the license expires, it's nearly always more profitable to make a new game than re-license an old one).
- Way too many 80's / 90's DOS games to list (basically there were a lot of very small "Shareware" developers who went out of business without being acquired and after 30 years, are impossible to contact / no longer work in the industry / some even passed away).

Just like the waiting lines in The Division to even get started. Do not neglect the importance of gaming meta, it's sometimes a bigger part of the experience than the aliased scenes on the screen.