EA games- need for speed series, FIFA and lots more Ubisoft- assassin's creed series Sony- god of war and many more and my fav-- crytek- crysis series!
Of course you can't choose one company to be the best "overall," for the fact that companies usually work under a specific team/director/etc. therfore most of their games are similar. Or a company makes mostly RPG's or another company makes mostly FPS' so on and so forth. You could rate a company solely based on volume i.e. Nintendo Super Mario Bros. (40.24 million copies sold) of one game OR total games Nintendo has sold as of December 14, 2009: 3.5 billion. As for rating a company off of game quality or interest level or personal love for the game, of course it's going to be opinionated. I'd have to say the three prerequisites I look for in a game company to be able to rate it as one of the best would be; my personal connection to it ( Do i love it more than another game from the same genre) it's affect on our pop culture ( Even my mom knows about Link and many characters from Final Fantasy) and lastly, since MOST of the companies make a sequel to a good amount of games, how does that company go about making it. Is it just as good or better than the first product they put out or do we have to play with a naked man in one of the MGS games?
All hail Sega for making Sonic! \\o/ First game ever was Sonic the Hedgehog in my SMD, and ever since that moment, i think Sega is epic win. But they suck after you see how Sega of America screwed up with Streets of Rage 3/Bare Knuckle 3.
And i also think Capcom rules. *loves the Megaman Starforce/X series*
And... I don't know which one of them is better D:
DICE makes some great games. (Battlefield) Ubisoft is also making great games. (Just, random, great games) Riot, is making great fantasy games. (Fx. League Of Legends) And at last, Blizzard Entertainment, who is making: Warcraft, Starcraft and Diablo.
Bungie (For there Halo Trilogy) EA Sports (For Fifa and NHL) Valve (If only they could count to three) Epic Games (For games like Gears of War im into 3rd Person)
bethesda (fallout, elder scrolls) infitiy ward (call of duty modern warfare 1,2, and soon to be 3) activision (call of duty black ops and world at war)