Both titles were ambitious games, but both had very rough or even poor launches. Both games had a lot of refunds after their releases. Both Cyberpunk and Fallout 76 also were very buggy and glitchy games at launch. While I think it's impossible to launch a game with 0 bugs, the state that the two games were/are in was quite poor. Finally, both studios have or had to face PR nightmares. Fallout 76 with the whole bag fiasco, CD Projekt Red trying to prevent refunds and prevent Sony from removing the game from the store.
You could argue that Cyberpunk 2077 does at least have a real story unlike Fallout 76, and a pretty good cast. But Cyberpunk 2077 was also hyped up even more, and because of how open Fallout 76's beta was, a lot of people sort of knew that the game would bomb out on launch.
So with all of this considered, which game do you think is a bigger dissapointment?