well they are still the developers of some of my favorite games. It's not like a different developer gets credit for their work because they are gone now.

Doesn't matter if there inactive now.

1) Naughty Dog
2) Retro Studios
3) Codemasters

1. LucasArts/Lucasfilm Games
2. MicroProse
3. Origin Systems

Irrational

Dma design / rockstar north

Atlus

1. Intelligent Systems
2. Nintendo
3. Square Enix

1.) Rockstar
2.) Nintendo
3.) Treasure

Someone post Sega please!!!  And Konami!!

1. Blizzard
2. Square (-soft)
3. Piranha Bytes

btw: Why are certain developers (Nintendo) always seen as a single studio, while others are separated into their different development teams (Sony, Microsoft)? Is it because the majority of Nintendo's first party is in Japan, while both Sony and Microsoft are more spread out?

Nintendo has seperate "parties" that develop for them. They're all considered to be Nintendo but they have a little bit of a different name. Mario goes to one "group" and Kirby goes to another. Retro Studios is also a first party "group" who develops for Nintendo. They are all under the same house name Nintendo and it's easier to refer to them as one big group rather than EAD 1 or Nintendo SDD. 

http://en.wikipedia.org/wiki/Nintendo (That'll give you a little better info.)