Of all time...
(1) Insomniac (a constant stream of great games and often as well)
(2) Naughty dog (again a constant stream of great games)
(3)enix (the great stuff put out during the snes to ps1 era ex: valkryie profile)
(4)square (ff3, ff4, ff5, ff6, secret of mana, chrono trigger need I say more)
(5) ingognito (twisted metal, and warhawk)