A Nice to Have
Graphics give a game style, make it more visually pleasing and make characters more relate-able. Though technically, they’re not a necessity for the game to function. Everything could be squares and circles and the game mechanics and such would run fine. Most developers would start coding with just basic shapes (maybe wipe up a stick figure if they felt like it) and make the game work first, then splash on the graphics after.
Icing on the cake
Personally for me, as long as the graphics aren’t horrible and hard to look at, that’s good enough for me. I’m more about whether the gameplay is good or not. It doesn’t mean I don’t care if the graphics are great – it’s more the icing on the cake. I’d rather eat a good cake with no icing than good icing on a bad cake.
Graphics are everything?
For some, this is true. If a game doesn’t even have graphics up to their expectations they won’t even look at it. That’s fine because the world is like that. No matter what people say, humans are programmed to judge a book by it’s cover because that’s what senses are for: they give us information. I personally don’t like it when some people focus too heavily on the graphics and the game becomes poorer for it. For some, a bad game that has good graphics is acceptable. I’m not one of those people.
Higher Graphics = More Strain
The higher quality the graphics, the longer it takes to load and the more strain it puts on the machine. Long loading times and frame rate drops are 2 issues that can come from this. In my opinion these issues are huge and should not be caused by something like graphics. I say these issues are huge because they take away from the game
Graphics are important
Never the less, graphics are important. Good graphics can also send a message to people that this is serious game worth your attention to some people. A different art style is also a way to differentiate your game from similar ones. They’re also expensive :)