Most TV shows (Anime or not) engage in fan service of some sort. Generally speaking, it means you give the audience exactly what it wants. That can mean anything from seeing a long-brewing relationship brew into a romantic one, or it could mean two characters finally having a brawl that highlights their powers.
In Japan, though, there's more permissive rules about nudity than there are elsewhere, so "fan service" often became synonymous with a nude scene involving female characters. The anime Super Dimension Cavalry Southern Cross (which is the second arc in the US version of the Robotech series) features just such a scene in the first episode, where the main female character is shown topless in the shower (which is why the Netflix version is TV-MA, while the original broadcast TV series merely cropped it out).
As the US markets grew, however, they were toned down to more "acceptable" levels of sexuality involving things like community bathhouses (more common in Japanese culture) or swimsuits. The Naruto series featured the "Sexy Technique/Jutsu" (link may be slightly NSFW), where the main character assumes the form of a scantily clad or even naked woman (with the key parts obscured).
Evangelion was almost certainly using it as a tease to boost viewership, since the original TV series really didn't push those limits very much (if anything, the series revolves around how timid the main characters are with each other). The movie End of Evangelion, oddly enough, went the other way with scenes like
a dying Misato kissing Shinji as a lover and remarking they can "do the rest later".
The Rebuild Evangelion movies have been even more racy with
Shinji entering Rei's apartment to return something to her. He winds up knocking over a very naked Rei and falling on her in such a way as to avoid showing anything.
Is it considered good?
It depends. Kotaku reviewed No Game No Life and noted this
Shiro is 11 years old in No Game No Life. In the first episode alone, we get two panty shots of her. Over the course of the series she is naked several times (though of course it is self-censored in one way or another); and while the only one that young, she is far from the only girl seen in varying states of undress.
And later
But used as satire or not, that doesn't change the fact that the fanservice, while never superseding the plot, is still a constant presence—and 11-year-old Shiro is a part of that.
Some shows lean heavily on fanservice to draw viewers, to the point where the plot can suffer. Most Anime that is considered "good" tends to be those with a solid plot.
