Do it like Heroine's Quest, which is a game inspired by Hero's Quest but NOT a fan sequel or ripoff of Hero's Quest.
The game actually does use a certain number of modified graphics from copyrighted products. For example, the heroine's sprite is modified from the heroine from Legend of Kyrandia 2, and the portraits are traced from photographs of celebrities. But it's always done in a tasteful, NOT lazy way, and the game otherwise has an incredible amount of original content -- most of all, the game is a genuinely good game in itself.
So it all depends on how you present your game. If you simply rip off Police Quest in a lazy way, essentially piggybacking on it, most people will show some disdain toward your project -- including the copyright holders who will send a certain kind of legal letter in your direction. If however you present a serious, interesting game inspired by a classic, then even if you happen to use a few copyrighted content (whether graphics or game mechanics), most people will show admiration toward it -- perhaps even the original game's creators! and hopefully the actual copyright holders will turn a blind eye.
The game actually does use a certain number of modified graphics from copyrighted products. For example, the heroine's sprite is modified from the heroine from Legend of Kyrandia 2, and the portraits are traced from photographs of celebrities. But it's always done in a tasteful, NOT lazy way, and the game otherwise has an incredible amount of original content -- most of all, the game is a genuinely good game in itself.
So it all depends on how you present your game. If you simply rip off Police Quest in a lazy way, essentially piggybacking on it, most people will show some disdain toward your project -- including the copyright holders who will send a certain kind of legal letter in your direction. If however you present a serious, interesting game inspired by a classic, then even if you happen to use a few copyrighted content (whether graphics or game mechanics), most people will show admiration toward it -- perhaps even the original game's creators! and hopefully the actual copyright holders will turn a blind eye.