Hollow/empty words (n.) or ring hollow (v.), sound empty/hollow fits the meaning of 綺麗事, as it explicitly dismisses the subject-matter as unrealistic and reflects the hypocrisy connotation of 綺麗事. However, it fails to reflect the connotation of how the subject-matter sounds great at first glance.
In this case, idealistic (adj.) can be used instead, to reflect both the superficial positive quality and the unreality of the subject-matter.
It's idealistic to put the happiness of other people before your own.
Putting the happiness of other people before your own - how idealistic that is.
It's idealistic to expect people to value personality over looks
Personality over looks - how idealistic that is.