Which games worth to grab under $5 ?

That entirely depends on what tickles your fancy.

Deus Ex and Thief titles are always fun and always go on sale for less than a buck.

World In Conflict is a pretty decent lite RTS if you want to focus on micromanagement instead of base building.

SimCity is always a good time.

All the Tomb Raider games are on sale for cheap if you want to rediscover those.

Far Cry 1 and 2 are pretty good if you want an FPS romp.

Master of Orion 1 and 2 are great space 4X if you're into that.

Jagged Alliance 2 is 99 cents right now. Everything else is weirdly priced and Unfinished Business isn't even on sale.

Just from what I played... Hm...
Anachronox, just check a guide for the collectibles to spare yourself the nasty pixel hunting.
Arcanum, if you watch for the bugs and check companion levels and locations first, to know when to get there so they won't be forever underleveled.
The Bard's Tale, for good fun.
Betrayal at Krondor, if you can deal with the trappings of the time.
Divine Divinity
Evil Islands, just note that easy is hard, normal is impossible.
Gothic 1 and Gothic 2, though 2 becomes so much more difficult with NotR installed, which the GOG version forces.
HoMM4 (yes, 4)
King of Dragon Pass (original version is available as an extra)
King's Bounty: The Legend
KotOR1 and KotOR2
Might and Magic 6
The Witcher 1, if you somehow missed it so far and don't want to do what otherwise needs to be done to still get it for free.

Thank you .
Any other recommendations ?

The game I would recommend most of all is Gibbous: A Cthulhu Adventure if you were interested. Both the basic and deluxe editions are 85%, which price tracking sites show as being an absolute all time low for this game.

I'd also recommend Neverwinter Nights if you like RPGs and don't own original non-enhanced Neverwinter Nights. Part of what makes NWN worth getting is the Neverwinter Vault as this is a game that was born to be modded, and you don't need Steam to download them. - https://neverwintervault.org


The below list isn't definitive as I just did a quick scan of the store and probably missed stuff. If you have any questions about a game here, ask away. Although if a game is an RPG and not mentioned here, I probably have an opinion on it and may have missed it being on sale.

Games under $5 that I would recommend based on having actually played them. If I don't own the game on GOG, I played the itch version (same as GOG), iOS mobile version (same but with touch controls) and/or played it a long, long time ago on a DOS computer far, far away in some cases.

Agent A: A Puzzle in Disguise
Balrum
Bastion (the soundtrack is also recommended)
Call of Cthulhu: Prisoner of Ice*
Call of Cthulhu: Shadow of the Comet*
Cat Quest 2
Costume Quest
Cthulhu Saves Christmas
Day of the Tentacle Remastered*
Divine Divinity
Donut County
Dungeon Keeper*
Dungeon Keeper 2
Grim Fandango Remastered*
Hidden Through Time*
Holy Potatoes! A Weapon Shop?!
Loom
Master of Magic Classic*
Master of Orion 1+2*
Might and Magic 6*
Nox
Reigns: Game of Thrones
Sid Meier's Alpha Centauri Planetary Pack*
Sid Meier's Civilization 3 Complete (although I would recommend Civ4 more but that is on sale for $7.49)
SimCity 3000 Unlimited
The House of Da Vinci*
Ultima Underworld 1+2*
VVVVVV*

* have not played the GOG version


I own these games and quite shamefully have not played them yet.
Beyond Divinity
Divinity 2
Divinity: Dragon Commander
Dragon Age: Origins
Holy Potatoes! We're in Space?!
King of Dragon Pass (got free off another site)
Sacred Gold
Sacred 2 Gold
The I of the Dragon


Some games under $5 that are sitting on my wish list that I actually intent to purchase for real, not maybe stuff.
Arcanum: Of Steamworks and Magick Obscura
Astrologaster
Chook & Sosig: Walk the Plank
Star Wars: Knights of the Old Republic
Star Wars: Knights of the Old Republic 2 - The Sith Lords


Games under $5 that I bought during the sale
Albion
Indiana Jones and the Fate of Atlantis
Indiana Jones and the Last Crusade
Gibbous: A Cthulhu Adventure Deluxe Edition
The Sexy Brutale

I sure hope someone finds this list useful, because I spent too long compiling it. Some of these I only bought, but I did play a fair chunk of the following. Some I loved, and others I liked to varying degrees or I think they're worth playing.

Point and click adventure games
Blackwell Bundle -70% 4.49$
Blackwell Epiphany -70% 3.19$
Broken Age: The Complete Adventure -75% 3.33$
Deponia -90% 1.06$
Deponia 2: Chaos on Deponia -90% 2.13$
Deponia 3: Goodbye Deponia -90% 2.13$
Deponia 4: Deponia Doomsday -90% 2.13$
Detective Grimoire -80% 1.21$
Gemini Rue -70% 2.55$
Gibbous - A Cthulhu Adventure (standard edition) -85% 3.20$
Gibbous - A Cthulhu Adventure Deluxe Edition -85% 4.00$
Irony Curtain: From Matryoshka with Love (standard edition) -80% 4.27$
Memoria -90% 2.13$
The Dark Eye: Chains of Satinav -90% 2.13$
Primordia -70% 3.19$
Resonance -70% 3.19$
Shardlight (standard edition) -70% 4.80$
Technobabylon -70% 4.80$
Virtuaverse -70% 4.80$
Whispers of a Machine (standard edition) -80% 3.20$
Whispers of a Machine Blue Edition -80% 4.06$

Platforming
Adventures of Chris -80% 2.67$
Apotheon -75% 3.74$
LIMBO -75% 2.66$
Foregone -80% 3.59$
Pinstripe -90% 1.49$
Planet Alpha (standard edition) -80% 4.27$
Out of Line -60% 4.61$
Prince of Persia: The Sands of Time -80% 2.13$
Prince of Persia: Warrior Within -80% 2.13$
Prince of Persia: The Two Thrones -80% 2.13$
Prince of Persia (2008) -80% 2.13$
Sundered: Eldritch Edition -80% 4.27$

Horror
Darkwood -70% 4.48$
Dead Space -75% 4.99$
Harvester -70% 1.79$

Role playing
Bastion -80% 2.99$
Dragon Age: Origins - Ultimate Edition -75% 4.99$
Dex -90% 1.49$
Deus Ex GOTY Edition -86% 1.04$
Deus Ex 2: Invisible War -86% 1.04$
Deus Ex: Human Revolution - Director's Cut -85% 3.20$
Deus Ex: Mankind Divided (standard edition) -85% 4.80$
Jotun: Valhalla Edition -80% 2.99$
The Technomancer -70% 3.19$
Transistor -80% 3.99$
This War of Mine (standard edition) -80% 4.06$
This War of Mine: Complete Edition -82% 5.05$
The Witcher 2: Assassins of Kings Enhanced Edition -85% 3.20$

Action
Hard Reset Redux -90% 1.99$
Metro: Last Light Redux -75% 4.99$
The Bureau: XCOM Declassified -80% 4.27$
Tomb Raider GOTY -80% 4.27$

Beat 'em up
Mother Russia Bleeds (standard edition) -80% 3.20$
Mother Russia Bleeds: Dealer Edition -80% 4.99$
Sleeping Dogs: Definitive Edition -85% 3.20$

Racing
Carmageddon: Max Damage -75% 4.54$
GRIP -85% 4.00$

Miscellaneous AKA "Adventure"
Haunt the House: Terrortown -80% 0.85$

Honorable mentions
• Shadowrun Returns and Shadowrun: Dragonfall - Director's Cut are both -75% 4.00$ right now, but I don't think they're worth it compared to Shadowrun Trilogy -75% 14.93$
• The Surge (standard edition) is -75% 4.00$ right now, but I don't know if it's worth it compared to either the deluxe edition or the dual pack with the two base games.
• The Witcher: Enhanced Edition -85% 1.27$ but you can get it for free through the GWENT Welcome Bonus. I also have a gift code to spare, if one of the forum regulars needs it.

Also recommendable:
Age of Wonders
Act of War: Gold Edition
Archimedean Dynasty
Blackguards: Special Edition
Clive Barker's Undying
Crysis
DethKarz
Dex
Driftland: The Magic Revival
FlatOut
Heretic + Hexen Collection
King's Bounty: Crossworld Goty
Mirror's Edge
Quake: The Offering
Rebel Galaxy
Red Faction Guerrilla Re-Mars-tered
Risen
Saint's Row IV: Game of the Century Edition
Space Pirates and Zombies
STAR WARS: Dark Forces
Supreme Commander Gold Edition
System Shock Enhanced Edition
The Elder Scrolls Morrowind Goty Edition
The Ultimate Doom
Unepic
Unreal Gold
XCOM 2

Frostpunk is now on sale, for a few hours, for $4.49. But it won't last long, so don't tarry.((;--))

I can't recommend Yoku's Island enough, which right now is less than $5.