All the way back in the original Xbox generation, we never actually got a proper version of Far Cry 1 on the OG Xbox console. Instead, 2004's Far Cry Instincts was a different take on the game (it technically served as a remake), and we had to wait another 10 years for FC1 to arrive on Xbox 360 in the form of Far Cry Classic in 2014.
However, it seems like there were definitely tests involved in bringing Far Cry 1 to the original Xbox back in the day. Just recently, a new Xbox Development Kit owner took to Reddit to share that they'd accidentally discovered evidence of an unreleased Far Cry port, and they provided a video that's unfortunately now been removed for whatever reason.
There are backups of this video appearing elsewhere though, such as in the tweet you can see below:
The original poster mentioned that they found this Xbox Development Kit in Germany, and they had to "do a double take" when they stumbled upon this version of Far Cry 1 for the OG Xbox. Some have advised that it could just be a development build of Far Cry Instincts, but the owner believes it's more likely "a dismissed port of the original Far Cry".
The majority seem to be backing up that suggestion as well:
Of course, none of this matters too much these days as Far Cry Classic is backwards compatible on Xbox One, Xbox Series X and Xbox Series S, but it's still interesting to see that Far Cry 1 was being worked on for the original Xbox!