A list would be good if gas prices aren't approximately at market level.
Also, wouldn't prices be a little bit lower if more sovereigns sold gas?
Absolutely. The US Government provides subsidies and tax breaks to the toon of hundreds of billions to oil companies. It also shields oil companies from liability like in the case of the recent oil spill in the Gulf of Mexico. The US Government also heavily regulates the refiniing and other use of petroleum and heavily regulates the transportation industry where most of the oil is consumed.
It is hard to say if the these government activity affect the price of oil upwards or downwards at any given moment. It is possible to say that over the longer term the government activities keep oil prices higher than they would otherwise be in the free market.