Super Mario Galaxy 2. That game was great, until the green star challenges start. Every level has a green star, which is hidden in the level. But they did a horrible job of hiding them. A lot of the time, they're right on the normal path. Sometimes, you can find them easily, but they're only mildly challenging to get to, like one that requires you to walljump off of a wall that disappears after five seconds. Each level starts out with the camera panning through it, showing you the highlights of the level, often giving away the green star in the process. One of them was right there, right next to you when you start. I think I just won't bother finishing.