Last night, Geoff Keighley released The Final Hours of Half-Life Alyx, a documentary 'story-book' detailing ten years of work at Valve. As well as spilling the beans on the latest game, however, Keighley's work revealed a host of Valve projects that never saw the light of day.
Many of those were Half-Life titles. Episode Three entered production in 2008, but the confines of the Source Engine meant that Valve couldn't figure out something innovative enough, and the project petered-out as devs moved onto Left 4 Dead. Later on Half-Life 3 was briefly a reality, but the Source 2 engine couldn't handle Valve's vision for it at the time. Two more VR shooters would eventually be cancelled, as well as a Ravenloft game developed by Arkane, before Alyx.
But other games have also fizzled out over the last few years. A Souls- and Elder Scrolls-inspired RPG project was started, but never really got going. Left 4 Dead 3 was birthed in 2013 but, again, Source 2 apparently couldn't handle the studio's desire to have "hundreds of zombies" on the screen at a time.
In the wake of Alyx, level designer Phil Co told Keighley that Valve isn't "afraid of Half-Life no more," suggesting that more games are on their way. It would seem, however, that most of the other abandoned titles mentioned in the documentary are likely to be lost forever.