Wow, earth shattering news here, turning off your PC when your not using it saves you a significant amount of money! What about factoring in cooling costs. High end gaming machines put out a lot of heat too. Since many gamers are using SSD's these days, sleeping your computer is great, they resume so fast. It's just common sense. I make sure everyone in my house shuts down or sleeps their machines at night if there is not a valid reason why they are on. It really does help.
The real problem with this list is where is the spec list? That dual or triple GPU machine, that is water cool, and has a huge overclock will use a ton more power then your i5, single GPU machine. Finding an average gaming machine is tough to do.