Utopia is a tradicional sci-fi concept or trope. Ussually it means a place where every problem social, political and moral has been resolved, either by politcal means or by technological (or magical if it's set in a fantasy world) development. Can be easly a isolated human society, an alien society or a future time where all the troubles and conflicts from present society are non existent. Writers use the concept of utopia to expose their own ideas about how to solve present days problems. If something is absent in a utopia is the idea of dissent, somebody who don't believe in the positive nature of the utopia.
Stories related to the utopia concept usually revolve around the ideas of: a foreing explorer who discover the perfect place and try to stay, but is rejected by the natives; a external menace than threats to destroy the perfect place; the dark secret of the utopia, mostly based in it past, how it was reached and upon whose bones was built.
Utopia as a literary resource it was used more in past times, when the technological development still offered the illusion of being a social panacea. Modern writers instead choose use Dystopia concept. Still both concepts can coexist at the same time in a shared universe.
Also the concept of utopia could be highly subjetive. It depends a lot of the point of view from any person: a perfect society for a person can be an oppresive regime for another. For example, a crimeless society could seem a nice place to live, only if you accept the brainwashing of potential criminals.
Comics example of utopia:
- Wonder woman: Paradise Island is perfect because is a society built only by women.
- Inhumans: inhuman society had banished racial discrimination among themselves
- Silver Surfer: Zenn-La was a perfect society where Norin Rad grew bored until he sacrified himself to save it from Galactus.
- Legion of Superheroes: the 30th/31st century earth is a perfect society thanks to Superman influence.
- DC 1.000.000: The Solar Sistem is a even more perfect society thanks to Superman influence.
- Star Trek comics: Technology made the mankind reach the stars and form alliances with another cultures.
- Superman: Pre crisis Krypton was a perfect society. The only reason to oppose to the rules is because you were evil. Notable exception: Jor-El.
- Multiversity: Earth-10 is seen as a nazi utopia; Earth-16 is a crimeless world thanks to the watch of the Superman Robots. Because of this, the offspring of superheroes had nothing to do.
- Magnus Robot fighter: The perfect future of Magnus is only threathened by the rebel robots.