I'm not talking about a Ubisoft-esque scenario where the released game looks worse than the beta/alpha versions, but games that actually came out with a certain graphical quality standard that got degraded over time with patches.
My example would be pretty much any early Source Engine game - particularily Half-Life 2 and Team Fortress 2.
The original release of Half-Life 2 had a quirky, but still human looking G-Man. His blue eyes were literally the first thing that made people back then awed by the Source Engine. When enemies got shot, the blood effects and stagger animations felt grounded in reality, like you were shooting an actual mass of a person instead of a cartoon. G-Man's eyes were retextured to look alien, HDR was later added, which, while a neat effect, clashes with the game's intended art style - making some areas brighter than originally intended. Textures also appear to have lost some detail in the most recent patch than they had in 2004.
Team Fortress 2 is similar in its degradation. The added implementation of SSAO and other lighting effects messed up how characters' faces were lit in the selection screen (now they look rather uncanny,) animations such as the revolver/medic's gun barrel rotating were broken and no longer play, texture details on certain buildings like the Red/Blue bases were removed and substituted with signs, leaving the original surfaces rather plain, water had 3D-looking ripples when you shot it that was replaced by a cartoony white ripple texture, and you used to be able to set a console command to use higher quality character models and textures than the Options menu provided with, before a patch came out removing/breaking those commands.
Are there any other examples of this in PC gaming, where something about a game's presentation got degraded after its initial release?