That might never even amount to anything, before they had financial backing of capcom...

Those are my favs:

-Nintendo
-Square-Enix
-Maxis (Sims 1&2)
-Namco
-Intelligent Systems (Paper Mario)
-Camelot (Golden Sun anyone?)
-Capcom.

3DO

-Nintendo 

-Square

-Enix

-Silicon Knights

-Square Enix

-Intelligent Systems

-HAL Laboratory

-Capcom

-Valve 

-SEGA

-Camelot

 It's really more on a game by game basis for me, and there are more. Maybe I'll look around more later.

First Party would be Nintendo, Third Party would be Capcom.

1-Level 5 (Gosh, am I the only one around here? Got all their games including Layton and Jeanne d'Arc, plus DQVIII and Dark Chronicle belong in the top 5 of most favorite games of all time for me)
2-Nintendo (Including their first party developers such as Intelligent Systems)
3-Marvelous (for the Harvest Moon franchise)
4-Tri Ace (underrated developer)
5-Namco Bandai (Tales of...)
6-Nippon Ichi (Disgaea for example)
7-Square Enix
8-Konami
9-Capcom
10-Gust

1) Nintendo.

2) Factor 5.

3) Intelligent systems.

4) Blizzard.

5) Free radical entertainment.

6) Clover studios.

7) Rare.

8) Seeds.

9) Monolith soft.

10) Square-Enix.