philchute.com/games/valve

Valve corporation was founded in 1996 by Gabe Newell and Mike Harrington. PC gaming is defined by their landmark 1998 title Half-life and the mods that surrounded it. Valve's follow-up titles rank among the best games of all time.

All of Valve's early titles are available in a package on Steam: Valve Complete Pack on Steam
This package sells for $65 but goes on sale for only $13: Valve Complete Pack on SteamDB

Half-life
Set the bar for action adventure games. There is a very high quality remake of this game called Black Mesa
Youtube video: Black Mesa Gameplay Launch Trailer
Youtube video: Black Mesa: The 16 Year Project to Remake Half-Life | Noclip Documentary
Youtube video: Black Mesa is Genius, And Here's Why
Youtube video: Half-life Fan Trailer
Youtube video: RetroAhoy: Half-life
Youtube video: Errant Signal: Half-life
Youtube video: A Thorough Look At Half-Life (Revised/Expanded)
Youtube video: Glitches and Tricks in Half-life 1
Youtube video: Half-life Adrenaline Gamer frag movie by Alex

Half-life: Opposing Force
Experience the events of Half-life as Army soldier Adrian Shepard.
Youtube video: Half-life: Opposing Force Trailer (Remake)

Half-life: Blue Shift
Experience the events of Half-life as security guard Barney Calhoun.
Youtube video: Half-life: Blue Shift Fan Trailer

Deathmatch Classic
Quake deathmatch ported to the Half-life Goldsrc engine. Soon to be remade in Source as Deathmatch Classic: Refragged.
DMC:R official discord: https://discord.gg/n2xpW9x

Counter-Strike
The original tactical esport retains a massive pub community and pug games are still played at all levels.
Youtube video: Where CS Happens (Where Amazing Happens) by EJA
Youtube video: eoLithic - The Movie
Youtube video: eoLithic - Oslo by Storm
Youtube video: The Story of Door Stuck

Team Fortress Classic
The Quake mod Team Fortress was an early port to the Half-life engine, and is still played to this day, with a small pub community and a diehard pug community.
Video guides: Nuki's TFC Learning Center
Youtube Video: 20th Anniversary Retrospective
Some oldschool skills movies:
Defrag and vriens TFC Skills movie
Skillout - Team Spirit - Plain

Day of Defeat
This class-based World War 2 mod remains one of the best gameplay experiences from the era, and retains a small pub community and a diehard pug community.
Pickups, tournaments, forums and info - Nineteen Eleven DoD Community
Youtube Video: Day of Defeat - A retrospective tribute to Half-life modding
Youtube Video: "Defeat". Valve's Forgotten Game
Youtube Video: STOP IT!!! [DoD 1.3] (funny clip)
Youtube Video: compLextity DoD (frag movie)

Ricochet
The beautifully underappreciated masterwork that is ricochet. Only a few players now, but occasionally a pub server takes off.
Ricochet discord: https://discord.gg/b2teuWM
Youtube video: Ricochet: A Deep Look at a Shallow Game
Youtube Video: Ricochet Mapping Tutorial

Counter-Strike: Condition Zero
The first retail release for the hit Counter-Strike mod. The singleplayer campaigns are still playable and enjoyable.
Youtube Video: VNN: The History of Counter-Strike: Condition Zero

Half-life 2
Raised the bar for action adventure games.
Youtube video: Half-life 2 Fan Trailer
Youtube video: Half-life 2: Series Trailer (Fan Made)
Youtube video: A Love Letter to the Source Engine
Recommended gameplay experience is the community made mod Half-Life 2: Update

Half-life 2: Episode One
First of three expansions for Half-life 2
Youtube video: Half-life 2: Episode 1 Trailer

Half-life 2: Episode Two
Second of two expansions for Half-life 2.
Youtube video: Half-life 2: Episode 2 Trailer

Half-life 1: Source
A remake of Half-life in the source engine. Recommend instead to play the Black Mesa remake, or the original.

Counter-strike: Source
A remake of Counter-Strike in the source engine. Divided the competitive Counter-strike community until the release of CS:GO.

Day of Defeat: Source
A remake of Day of Defeat in the source engine. Opinions about the superior game are still divided.

Team Fortress 2
More than a remake, this was a transformation of Team Fortress. Originally a retail product that transformed to the new market of Free-to-Play games, TF2 continually transformed itself through content releases as it became one of the most widely played and influential games of all time.
Youtube video: Errant Signal: Social Spaces & Payload Races
Youtube video: What happens when overwatch players play TF2
Youtube video: the best competitive game that nobody plays
Youtube video: The soul of TF2 in one clip

Left4Dead 1 & 2
The best co-op zombie survival horror games of all time.

Portal 1 & 2
The best comedy action puzzle games of all time.
Youtube video: Portal Teaser Trailer
Youtube video: Portal 2 Teaser Trailer
Youtube video: Portal 2 - Full Co-op Trailer
The short game Aperture Desk Job is set in the Portal Universe and is playable on PC using a usb gamepad.

Counter-Strike: Global Offensive
CS:GO was released as a retail product in 2012 but was converted to free-to-play in 2018, and has become one of the largest esports on earth.
Youtube video: The Story of CS:GO: The Game That Never Dies
Youtube video: Legendary Astalis' dev1ce - CSGO frag movie
Youtube video: 6 year old kid wins CS:GO round
Youtube video: CS:GO - Where Amazing Happens

Half-life: Alyx
Half-life and Valve move to virtual reality in the latest title. Not included in the Valve Complete Pack. Half-life: Alyx on Steam
Youtube video: Half-life: Alyx Trailer
Youtube video: Half-life: Alyx Changed Everything (Spoiler free)