Technically speaking, a cleanroom reverse-engineered program isn’t illegal (this is how IBM PC clones were allowed to exist), at least in the US.
On the other hand, since AI cannot hold a copyright, the prompters cannot sue if, say, Sony or Microsoft just take their code and sell it.
Most decompiled games need a copy of the original game for assets (graphics, textures, etc) since those wouldn’t be recreated via AI, and shipping with them would be copyright infringement.