Blizzard and Nintendo.

They are the best of the best in their respective area.

My top 3........... Lifetime developers

1. Sega.... Home of Shenmue, Virtua fighter, Sonic, Streets of rage, Shinobi ect ect ect
2. Nintendo...... Home of Mario, Zelda, Donkey kong ect ect ect
3. Treasure....... Home of Guardian heroes, Ikaruga

Honourable mention......... Capcom, home of Resi evil, Devil may cry, Street fighter ect

Konami for me: Suikoden+PES+MGS+Silent Hill, no contest

After that, Sony, Atlus and Square, in that order

Nintendo. The world wouldn't be the same without Mario, Zelda and Metroid.

Nintendo, hands down is the best game developers ever!

The Nintendo studios that make Mario, Zelda, Smash Bros, etc.

nintendo is NOT the best dev. when was the last time they made a new ip that didnt have the name wii in it? there are many great developers, there is no "best"

Blizzard then Nintendo

If you go by sales its Nintendo.
If you go by money its Nintendo.
If you go by most innovated its Nintendo.
If you go by great games in different genres its definitely Nintendo.

Nintendo-The only developer in the world that only puts AAA titles.

Nintendo has developed:

The best Platformer ever (Super Mario Galaxy) and The most respected Platformer franchise ever (Mario)
The best First Person Adventure ever (Metroid Prime)
The best Action/RPG ever (Legend of Zelda: Ocarina of Time)

They also have the biggest pile of $$$ in the history of videogaming.