Well, some 5-year-olds have watched a half-dozen Marvel movies that have very similar content. That’s why I’m giving details onto what’s age-inappropriate about the Portal games so the parent can make an informed decision.

edit: And if just the constant black comedy from GlaDOS is okay, but the blood-splatters when you get shot are concerning, there are ways to disable it (although they’re console-commands and not part of the menu). In Portal 2 the blood was removed altogether because the game didn’t really need it anyways.