
Now I also know that some Tiberian Sun mods/TCs have become stand-alone (like Twisted Insurrection), however it's often hard to find out if there had been non-standalone releases of them, or they were conceived as standalone games from the very start.
League of Legends (evolved from Defence of the Ancients).
The Haunted: Hell's Reach (originally The Haunted). Antichamber (originally Hazard: The Journey of Life). Damnation (evolved into an Unreal Engine 3 game). LTKTBM (based on the Action Quake 2 TC). CodeRED: Battle for Earth (originally CodeRed). Vikingr (does not require Warband to be installed but asks for a license key). Mount & Blade: With Fire & Sword (originally a commercial TC/add-on Mount & Blade. Black Mesa (started as two separate mod projects). Team Fortress Classic (based on the Team Fortress TC for Quake). Gunman Chronicles (initially a Quake TC that first moved over to Quake II and then to GoldSrc). Die Hard: Nakatomi Plaza (went over to GoldSrc and then to LithTech). Action Doom 2: Urban Brawl (a prequel to the Action Doom TC). Tiberian Sun Reborn (originally C&C Reborn). Red Alert: A Path Beyond (originally Renegade Alert). In some cases below, however, a fully stand-alone game was preceded by a mod/TC with a similar theme or storyline. The criteria for picking games were as follows: 1) initially there has been a requirement that another title, of which the game in question is a TC or mod, needed to be present in order to run the game, and 2) eventually said requirement was dropped, making the game in question stand-alone. No idea if this is because of the general level of popularity of the FPS genre or some other factors have played a role as well. Probably not very surprisingly, what I managed to find so far are mostly FPS games based on popular engines (id Tech, GoldSrc, and the more recent UDK), with but a few titles from other genres. Eventually though I started to discover more and more of such games, and decided to make a list of them. For some time I used to think that total conversions of video games that eventually became separate, stand-alone titles are few and far between, as I knew only of a couple examples, like NAM and Gunman Chronicles.