I think it all depends on what sort of game you have, specifically if it is story driven or immersion/exploration driven.
Halo Reach is story driven and would have absolutely benefitted from a voice. Mass Effect was primarily story driven and the voiced protag worked great.
Fallout 4 is the opposite and a silent protag would have been better as silent, like in Fallout 3 or Elder Scrolls games.
I have a very complex rating system that I apply to every film I see. It ends up as a score out of 100, built up from scoring points in different categories.
I subdivide into 3 groups first, Enjoyment (50pts available), Quality (40pts available), Rewatch-ability (10pts available). Most of these are subdivided in some fashion, such as Quality: Writing, where up to 5 points can be awarded.
Here are 3 examples of scores as I record them.
The Fellowship of the Ring 92 (E48 Q36 R8)
Mary Poppins Returns 72 (E43 Q25 R4)
GI Joe: Retaliation 42 (E23 Q17 R2)
Most films I see score above 40, so it's a fair argument to say there is a dead zone in the rating system, but in reality a film should reach a bare level of quality so scoring under that threshold is a real indicator of a something really shit.
Update: Regarding your Avatar question. My system allows an individual's personal level of enjoyment to be scored in addition to the fundamental quality in a given film, so even a film like Avatar that you don't like as much now will still be able to get a respectable score from the other categories.