After a little consideration my own top 5 are:
1. Nintendo (If we can count all their development studios as one then this isn't a very hard choice for me)
2. Rare (pre-microsoft)
3. Capcom
4. Konami
5. Bullfrog
Wii code: 1534 8127 5081 0969
Brawl code: 1762-4131-9390
Member of the Pikmin Fan Club