You can probably fill up on 200 calories of broccoli, but don't expect to be full after 200 calories of cheese. A new video by AsapSCIENCE (above) depicts 200-calorie versions of common food items and it's pretty clear that portion size varies widely depending on the food you're eating.
The video has also a good description of exactly what a calorie is and how all calories aren't exactly created equal. For example, there are more calories per liter in whole milk than there are in Coke. However, whole milk offers nutrients and healthy fats, whereas Coke does not. The same thing goes for whole wheat bread versus white bread.
In short, while counting calories can be important, instead of thinking how much you're putting in your body, you should be thinking about what you're putting in your body.