Yes, this is in most cases a violation of copyright.
While many jurisdictions offer exceptions for fair use in specific applications (eg. education or parody), these don't prevent the original creators from suing you — they're just a form of argument you could try to use in defense. Even if you were technically in a permissible use case, the cost of arguing it in court alone might be enough to seriously threaten your business.
As a general rule of thumb: if you didn't make it or obtain explicit permission from the creator to use it in your game, then it's not your content to use.
Or more simply: don't steal other people's work, please.
(I am not a lawyer and this post is not legal advice)