If we're ignoring the steam greenlight crud and only focusing on games from big/known studios, I'd say Silent Hill HD Collection. Seriously, how do you mess this up? This should have been the "ultimate edition" with everything running smoothly, but no. We got a far inferior version of all the games. This collection was well known and loved so it had hype, and it ended up being a technical mess.
For films, I'd say Star Wars, the phantom menace. While true AotC was probably worse, the level of expectation and hype for the return of Star Wars was met with a huge thud shortly after the opening shots of TPM.