No Nintendo EAD, Sega WoW, From Software, Insomniac or Bungie? Fail.

1. Santa Monica
2. Naughty Dog
3. Quantic Dream
4. Bioware
5. Insomniac
6. Nintendo
7. 2K/Take two Rock Star
8. Epic
9.Guerilla games
10. Ninja Theory

Nintendo

I have enjoyed others along with some of the smaller studios.

1. Square-Enix
2. Naugthy Dog
3. Bioware
4. Nintendo
5. Bungie
6. Infinity Ward

Ugh, too hard!  I'll do top 5...

01 Nintendo (Super Mario, Legend of Zelda, Mario Kart)
02 Capcom (Monster Hunter, Street Fighter, Resident Evil)
03 Atlus (Shin Megami Tensei, Trauma Center, Etrian Odyssey)
04 Valve (Half-Life, Left 4 Dead, Portal)
05 Level-5 (Dragon Quest, Professor Layton, Inazuma Eleven)

It saddens me not to see Rare more present this gen.

1 - Nintendo

Software was what rocketed the Wii

2 - Blizzard

One word: WoW

3 - bethesda

The Elder Scrolls IV Oblivion and Fallout 3 are absolute milestones in gaming and really made me realized how much it has progressed.

4 - Valve

Their multiplayer FPS are in a league of their own. L4D and Team Fortress are excellent at being balanced games that are simply pure fun.

5 - Bioware

Mass Effect is a big name this gen. Personally, I think Dragon Age Origins is over ten times better.

People overlook Developers like Cing,Atlus,Grasshopper studios.
They have put out some of the best stuff this gen,but get no spotlight.

Cing,Atlus,Grasshopper studios

Not sure that everyone realises the OP says this gen. Some odd choices like Capcom???? Square Enix????????

Anyhow.

1. Bungie. Purely because no other game has been in my console as much as a Bungie game. That instantly makes them my choice number 1 obviously.

2. Bioware. They have created this gens best new IP. And it's a series. The first was fantastic and reviewed well even eith tech issues. Th 2nd was a masterstroke of the best RPG ever made.

3. Naughty Dog. These guys again have created a fantastic new IP this gen. Uncharted was good, but they excelled to the top with Uncharted 2.

4. Epic. Another dev that has brought a new IP. And again both games in the series were fantastic. The first true nex gen game we had.

5. Bethesda. These guys are on fire this gen. Truly Oblivion was awesome and Fallout 3 shut the doubters up. Only one RPG has beat it. Sorry Bethesda, Mass Effect 2 is king.

6. Guirella Games. Some may not agree with these guys being here. I know they have only made KZ2 this gen. But against all odds ( Lets face it KZ1 was a mess ) these guys produced a fantastic FPS fo PS3. One which Sony fans can be proud of.

7. Turn 10. 2 games this gen. Both a must for sim fans. Forza 3 will be a year old soon. And it's currently the best sim racer ever made for consoles. Well done.

8. EA. These guys deserve to be in the top 10. For years they fell short with Fifa. And now, Fifa is the better game. They have listened to fans and answered. They have also released other great games this gen.

9. Nintendo. IMO there games are not as good as yesteryear. Everything is dumbed down. But still enjoyable to play. Mario Galaxy was great but not the best Mario game.

10. Ubisoft. These guys are making good games almost everytime this gen. You know their roster and a new IP. Nuff Said.

PS. I have not included Infinity Ward. Why? Although I like their games. They arent great. And as devs they have used some cheap tricks. Cmon IW is singleplayer Respawning a need? Maybe have a look at your AI or level design. And the multiplayer falls short of both KZ2 , BFBC2 and Halo imo.