I personally think of board games as a graphic design expression. I know there are good games hidden underneath bad or dry art, but I can't interact with them if they don't look good to me.
Regarding pieces, I don't care much for plastic or wooden pieces, I care for things that make sense in terms of readability of the state of the board, and if a game comes with ultra-detailed miniatures but they are all gray, I'd rather have cardboard stand ins that help me differentiate them.