" Also, I am sure that 2000 calories of steak isn't the same as 2000 calories of rice, or 2000 calories of soda."
Well, that depends on what you mean. The soda probably would not be very satiating, and you're probably be hungrier. It does not have the protein of the steak, nor the fiber of the rice. But weight-gain wise, you'd gain or lose the same amount of weight so long as your total calorie consumption was identical.
It's just thermodynamics. A calorie is a unit of energy [Food calories are : the energy needed to raise the temperature of 1 kilogram of water through 1 °C], your body takes a certain amount of energy to do all its tasks, and the excess is laid down as fat, because fat is the most dense way of storing excess energy your body has. So, from a "fat-building" standpoint, 2000 calories is 2000 calories. Otherwise, they're pretty different.
Just for fun, let's look at the nutritional profiles you suggested:
Rice: around 1570 grams of rice gives us 2000 calories, 41 grams of protein, 68% of your daily sodium ,etc.
Steak: around 960 grams gets you to 2003 calories, with 244 grams of protein and 29% of your daily sodium.
Soda: about 14 and 1/4 12oz cans of the syrup would get you to 1995 calories, with no protein, but 185% of your alloted carbs.