Art and graphics in-game are one of those: “I know how to judge it when I see it” standards.
Cover art for all games is essential in my opinion.
Supplemental art, such as maps can make or break a game as well but are not as necessary as cover art is.
“Informational” or “teaching” art can help a game build immersion and connection with their audience - especially in areas that people may not be familiar with. Including pictures of dinosaurs in the latest release would have added a lot of value to the game, to provide a relevant example of this type of art.
Then there are the more subjective art categories such as thematic art. In strictly defined genres, ( ie. anime and film noir) the art can be essential to the game’s success. Some games, like Hong Kong Blood Opera by @Jose_Garcia would benefit greatly from showcasing the genre’s typical art-style.
Art can also be essential to establish name brand identification in a game. WoW’s oversized shoulder armor and cartoon sized swords are an example. When “Conan the Barbarian” is mentioned most people have expectations on what the game will be like - part of those expectations are a result of the original art established for the IP and any break from that tradition is open to criticism … Funcom tried breaking from that tradition in their games but got caught up in such push-back.
My opinion on character art is evolving. The reason why it is evolving is because I have become aware of a condition called prosopagnosia - face blindness.
This means (as far as I understand) that descriptions alone may not be enough for some to be able to picture and retain an image of a character.
In text-based games but for the most part I would rather allow a reader’s imagination to “paint their own portrait” of the NPC. Since learning about this condition, I am more open for the major NPCs to have accompanying art, so that those who do suffer from face-blindness will have a graphical reference to refer to as needed.
One of the reasons I feel Community College Hero by @Eric_Moser works better than other super-hero stories is because he doesn’t overplay the art aspect of the super-hero genre. It allows people who enjoy different aspects of the genre to enjoy the game, without pushing other aspects that they may not enjoy in their face.
The audience can imagine the CCH story taking place in a darker, grittier Middle America or the audience can imagine a more campy, comic-book feel of Middle America. It is left to imagination. Once the author takes this ability away by defining everything in art, the audience is forced to accept or reject what the author’s vision is. This could cause loss of sales, if the vision presented is different than that which could be accepted.
tldnr: Each project has different needs and should be judged differently because of those needs.