It really depends on your goal and how blatantly disrespectful you are. For example, create a Mario style game using actual copies of their graphics and share this amongst a few friends. It's not like to draw much attention from any one. Take that game and post it on YouTube as a game making tutorial and don't allow any advertising so you do not profit from it. Still, not likely to ruffle many feathers, at least until it become popular. Ok, now try putting an advert in the middle of the video that promotes a range of Nintendo branded merchandise that you alone have created and have no sub-licensing agreement in place with Nintendo. This will not go down well. Basically does anyone profit from your efforts? If yes, then do your efforts rely upon the intellectual property rights of others. If yes, then don't do it! It is nothing more than common sense. At the end of the day lets say you come up with an idea. You create a character and a game idea that no one else has ever thought of. You put years worth of effort into it and thousands, if not millions of $$$ into developing the 'brand' behind that design. Then someone comes along and uses your artwork, your game design and your story writing with little other creative effort and profits from it. How are you going to respond? Let that be your moral compass.