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)
I'd have to say DICE since BF3 is coming out tomorrow and is going to be awesome. Valve is great, and 2k is pretty good mainly for Bioschock.
The problem I have here is that I see a lot of people saying Activision. Let me just remind you that Activision is not a game developer, they are a publisher thus they don't make the games. If they have concepts for a game they send it to a studio. When the game is ready they take care of packaging, distribution, and marketing.
I could go on about the conglomerates of EA and Activision, but you can find that for yourself if you'd like to educate yourself further than being the guy who buys everything they're selling just for the name.