I can't really explain it with still screens, but my submission would be Guitar Hero: World Tour. Band play was a complete fucking disaster because the game goes out of its way to make it impossible to tell how well an individual player was doing and, conversely, how close they were to failing out. Also awful was the lyrics display for the singer, because instead of using the industry standard needle to keep track of how close you to being on pitch, they adopted this strange box setup that blocked out the pitches when you were on key and jumped around like someone going crazy with a pixel editor otherwise. And don't even get me started on the song selection menu...
Thankfully, they started to kinda get their shit together with Guitar Hero: Metallica, so GH:WT was a one-off in that regard, but it still boggles my mind how unbelievably poor it was, even without having Rock Band as a comparison.