I have sometimes heard people say that they like certain artists because those artists cover their drawings with lots of detail. There' nothing wrong with that opinion, taste is totally subjective and I don't believe there's a "right and wrong" with art. Personally I tend to disagree with the idea that blanket detail is a good thing, though, because I think smart artists make choices....and covering everything evenly with detail is not really making a choice.
It seems that as a general rule, contrast is a key to creating works of art that are interesting to look at, and of course a contrast is created when you have blank spaces against areas of detail, as opposed to a piece of art that is all detail, or a piece that is all blank open areas.
I always hate to pick on artists, especially really good ones, and it always gets me hate mail, but as an example of what I mean, sometimes I feel the great Jack Davis uses too much detail. At least for my taste.
If it wasn't for the colors applied to this drawing, you wouldn't know where to look. The level of detail is really high (and evenly distributed) on every inch of the piece.
I can only imagine that the reason some people love a high level of detail is that some people like to look at a drawing and really spend some time with it, absorbing every detail and finding little jokes hidden by the artist. Personally, I don't. I really like art that makes a strong statement and one is which each area has an order of importance...I like it when an artist is clear about where to look first, and then where your eye should go secondarily, etc. I like it when artists make strong choices and direct your eye through their choices. To me, this Davis cover below is a mess. The values and levels of detail are all the same.
Here's a much better Jack Davis, in my opinion. The figure in the foreground has the most detail and the most black-on-white contrast, so my eye goes there first. Then the figure at the top left has the second highest level of detail and some black-on-white, but less than the central character. The rest of the piece has no areas of black-on-white and has thinner line work so it doesn't draw your eye until you've seen the other two more important figures that tell the story. The pile of bodies and street scene are just background that contribute to the idea, but don't overwhelm the more important figures.
That last piece leads nicely into another thought about detail...detail can be very helpful at getting your viewer to look where you want them to look.
It's always a challenge to get the viewer's eye to go to the part of a drawing (or painting) that is exactly where we want them to look. And putting detail where you want to attract the eye is a good, foolproof trick. And so, for that to work, the areas where you don't want the audience to look need to be blank, or at least have less detail than the areas where you want them to look.
Detail can also be helpful for indicating scale....things with a lot of detail tend to look bigger, if they're placed next to objects with less detail for contrast.
Detail also makes things seem closer to the viewer. Blank areas, by contrast, feel farther away.
Another thing I've heard people say is that drawings look more "realistic" to them when there's more detail on every bit of the drawing...but again, I don't see it that way. I've often read that our eyes don't even work that way. When we look at things in real life, our eyes (supposedly) see whatever we're focusing on in great detail, but the rest of our field of vision is slightly blurred and out of focus (and it increases more on the edges of our vision). If we saw everything in stark detail all the time we'd probably have a headache all the time (our eyes seem to work like our ears - we filter out most of the sound we hear and just focus on what's important).
To me, what makes a drawing look "realistic" to me has more to do with proportions. Personally I always found, for example, Milt Caniff's drawings to be very "realistic" because the proportions are pretty "straight": not only are the figures a realistic height, but the features of the face are realistically small, not really caricatured (although he does have some cartoonier characters from time to time). I like Caniff's level of detail, it feels right and not like he's trying to overdo it in an attempt to be "realistic". He lets the proportions do that for him. Also, he uses silhouette in a smart way to minimize areas of detail. It feels like he's making choices and using design to caricature reality, not try to capture it verbatim.
Usually when artists draw pretty girls they don't put a lot of detail on their faces to keep them looking young and pretty. Too many lines on the face can start to read like wrinkles, or blemishes, or sweat, etc. So usually it's proportions that artists have to use to get that "realistic" feeling.
In this Bernet drawing below, you can see the difference between how many lines he uses on the men's faces and how many he uses on the girl's: hers has much less detail. But he uses a lot of lines on her hair and clothes to balance it out and so they both feel like they belong in the same drawing.
These Alex Toth pages have a great balance of blank black areas, blank white areas and areas of controlled detail. As an overall design, they're very easy to follow and pleasing to the eye because they have a good balance of blank areas and detailed areas.
Some more good examples, by Quentin Blake and N.C. Wyeth.