Bethesda have made every Elder Scrolls so far: Arena, Daggerfall, Morrowind and Oblivion. Obsidian developed Fallout 3 after the collapse of Black Isle. Bethesda published Fallout New Vegas however, which is where the confusion is starting I think.
How about That Game Company.
The guys that made Privates? Or was that a different company?
2K Games for making Civ
2K Games published Civilization, Firaxis created it. Hence "Sid Meier's Civilization". Sid owns Firaxis not 2K.
My favourite games company? Epic Games for developing Unreal Tournament, Gears of War and undertaking the revival of the 2010 All Points Bulletin. I'm quite temperamental when it comes to my favourite games and games companies. Second I might choose Bethesda but I'm really not sure.