Sorry, I can't keep to 3 but, roughly in order, here they are -

Naughty Dog - My avatar says enough

Rockstar North - I know it has received some criticism, but I still think Grand Theft Auto IV is one of the best games ever, and I am replaying it now, and the game is incredible, the amount of work they had to put into it, and now they are following it up with the Lost and the Dammed, which while I can't play (though my fingers are crossed!) looks like a great addition

Infinity Ward - Call of Duty 4 was the best first person shooter I have ever played, and I doubt KZ2 will live up to it, it had an incredible single player mode, and then great online, I can't wait for what they have coming at the end of the year

Insomniac - 3 high 80 rated games already, plus Quest for Booty. Though the Resistance series is not my favourite as I am not a great fan of arcade shooters, they are doing a fantastic job for Sony, and I can't wait for their next game

Criterion games - Seriously, a year of free content! The only problem is that I imported my game, so I can't get the premium DLC, but what they are offering this year does look incredible

Media Molecule - Creating a great game, and following it up with great DLC, I can't wait for more level packs that we know are coming

Bioware - While they have only made 1 game, it was a fantastic game, unlike any other I have played, and I will be spending a lot of time on this game in the summer, and hopefully they get rid of all the small flaws for the sequel

- Naughty dog: I agree with what you said.

- Insomniac: +1 once again

- tie between ubisoft, EA, SE and GG: ubi for assassin's creed and PoP, EA for their great new franchises, SE for FFXIII and GG for KZ2 of course. Right now I'd say ubi, but later this month, probably guerilla games lol.

Sega is a good contender too.

Above I just listed my favourites I didn't notice it was supposed to be a top 3. So here they are, my top 3 publishers/developers:

Sony Computer Entertainment: Gran Turismo, Resistance, Heavenly Sword, Ratchet/Clank, Motorstorm, Warhawk, Uncharted, SOCOM, LittleBigPlanet, God of War III, MAG, Killzone 2, Infamous, White Knight Chronicles! Holy fuck I jizzed twice while making that list.

Ubisoft - Assassin's Creed, Ghost Recon, Rainbow Six, EndWar, Far Cry, Prince of Persia, Splinter Cell. How could they not be in the top 3?

EA - Say what you want but the gaming industry wouldn't be the same without EA. Crysis, Fight Night, Godfather, Madden, NHL, Dead Space, Need For Speed, Rock Band, The Fucking Sims!

Naughty dog. Loved Crash games, Uncharted

Capcom. Street fighter, Devil may cry, Resident evil.

Insomniac. Resistance, Ratchet

Infinity ward. Call of duty 4

Santa monica. God of war

Edit: Not playing too many Nintendo games now but who doesnt like Mario.

I messed up again, its devs not publishers.

Top 3 Devs

1. Rockstar North (GTA)

2. Infinity Ward (The Good Call of Duty games)

3. Insomniac (Resistance and Ratchet & Clank

BioWare (Mass Effect)
Valve (Portal, Left 4 Dead, Team Fortress 2)
Harmonix (Rock Band, Guitar Hero)

Bethesda (Oblivion/Fallout 3)

Sega (Valkyria Chronicles)

Nintendo (SMG).

My top three of this gen are (aside from Nintendo):

1. Vicarious Visions
Much is made of Harmonix and their supposed brilliance- but one relatively unknown dev was able to completely trump (some would say, embarrass) them by creating a rhythm action game for Wii with full online play, quickplay options and fully-fledged DLC, at a time when Harmonix said the "technical limitations" of the Wii prevented it from being done, and put out a lazy, half-assed Rock Band port devoid of all such features. At the same time, VV also proved many doubters wrong by making a DS Guitar Hero -at the very least, a playable portable realization of the concept- and at best, a brilliant shrinking of the GH package.

2. Criterion
A full year of free, game-changing DLC. Pretty hard to fault, especially when it adds to one of the most bold and innovative racers for years.

3. Studio Liverpool
Two words: Wipeout HD.

1. Bungie: No other developer can make a console multiplayer setup like bungie and their matchmaking system and multiplayer are second to none. All their games have 'a 10 year lifespan' because they are just fun for that  long.

2. 2k marine/boston(which ever made bioshock): Heres a developer that created a game (a shooter no less)with no multiplayer , not that great graphics and little to no hype and made a game that is more critically acclaimed than halo 3 ,gears, mgs 4 ,lbp,fallout. Heres to hoping their sequel can surpass their masterpiece

3. Bioware: This studio basically has the midus touch where everything they touch turns to pure gold and whatever platform you play their games on you can rest assured you are playing a top quality game that is second to none in storytelling for its time.

Naughty Dog - Uncharted is the only game this gen I have went back to time and time again.

Kojima Productions - Metal Gear Solid 4 was brilliant, the only gripe is the stupid Konami ID crap for online.

Evolution Studios - Both Motorstorm games this gen have held my attention for at least 45 hours a piece.

Honorable mentions;

-Insomniac - minus Resistance 2, they have been one of the most productive teams in the industry.

-Epic - Gears of War has given the Xbox brand a second must have exclusive.

-Criterion - We all know just how well they have kept Paradise city feeling freash, and even a year after launch.