They are not remasters, but Thief fan missions, some of them are truly amazing, there have been several hundreds of them released over the last 20 years and are still actively made. For me it started with Thief 2X: Shadows of the Metal Age, it was a very ambitious and lengthy fan project that was released in mid 2000s. Some of the fans are so talented that the original Thief games now look almost amateurish.
Also Unreal saw a big fan project released in Operation NaPali in 2007. Unreal had lots of fan maps and campaigns too but the community was much smaller and is almost dead now unlike Thief.
I have played a lot of fan made content for other games too like Deus Ex, Max Payne, Half-Life, Heroes of Might and Magic 2&3. It is one of the things that sets PC gaming apart
Deus Ex (2000) - a game that pushes the boundaries of what the video game medium is capable of to a degree unmatched to this very day.
