I'd give you that....if games when Fallout came out all had voice acting.
Fallout 1 voiced Tandi, and upon meeting her father or her you would not have known she was an important character (Fallout 1, not Fallout 2).
It's a moot discussion anyways, as we don't know what BIS/Interplay would have done if they could have afforded the voice all the lines.
Sin City's is artistic because all movies are in colour now. How many would have lauded it's artistic sense if it was going up beside the very first movies that had full colour and the wow factor of the full colour? Wizard of Oz milked this like crazy, starting the movie in black and white, and then going BAM, look at all the beautiful colours.
Fallout's voice acting was cool, but imagine your reaction if every line in the game was spoken. To say that you wouldn't care is bogus based on hindsight IMO.
Furthermore, since you like to state that developers give secondary characters voices so that you can hear what they sound like, then Baldur's Gate has the same thing. When you initiate conversation with every character they make some sort of audible noise...it's just that their lines of dialogue aren't spoken. You still know what they sound like.
But imagine how alive the world would be if every person was voiced in quality....