[haunter]

That entirely depends on the games you want to play. Check the most played games on Steam and how many of them are available on GOG. 1 out of 10 or even less.

[AngryData]

To be fair many of those are multiplayer games with required updates and anticheat.

[haunter]

30 is f2p from the top 100

From the remaining paid 70 there are 2 softwares (Wallpaper Engine and Crosshair X)

From the remaining 67 there are 2 versions of ARK Survival and GTAV so we can count those once.

That leaves us with 65 games

From the 65 games 13 are available on GOG:

- Baldur's Gate 3

- Cyberpunk 2077

- Factorio

- Kingdom Come: Deliverance II

- Mount & Blade II: Bannerlord

- Project Zomboid

- RimWorld

- Stardew Valley

- Stellaris

- Terraria

- The Binding of Isaac: Rebirth

- The Elder Scrolls V: Skyrim

- The Witcher 3: Wild Hunt

That’s 1 out of 5 which is better than I've guessed (1 out of 10)