Back before they were gobbled up by Sony, Psygnosis (sp?) had a few gems that were technical marvels and quite fun to play. Other studios included Koei (I adored the amazing Japanese war simulations on the old NES) and Hudson.
Last but not least, Nihon Falcom... Famous for the Ys series of games over the years and blew me away when I first invested in the beast, the original TurboGrafx CD. Sure the Sega consoles did get a little Ys love but I'm happy that these games have been re imagined on the PSP/Vita. I dream of a native Ys title for that handheld monster.
Others I still am fond of are...
EA as a publisher... (flame suit is on but how can anyone hate the Mass Effect series and Need For Speed?)
Developers alone...
ADK - developed almost exclusively for the Neo Geo and the wonder (and hard as fuck) launch title Magician Lord and other great games on the platform.
Chair - Known for the Infinity Blade series on iOS.
TellTale Games - Makers of the Strongbad series and the crown jewel, with a full cooperative effort from Universal Studios no less, Back to The Future series. If you haven't tried the demo, give it a shot if you love the movies, every bit of the game is sewn together with incredible attention to detail. Even the original soundtrack.
Sony Santa Monica - Without them how else could I splatter blood with a grin in God of War
Epic Games - Gears of War and its sequels... 'nuff said there.
Bungie - Originally a Mac developer only who brought us Halo. Without the bold move of forking over a shitload of money, the FPS genre wouldn't be much of a success on consoles. Halo was actually planned to be a Macintosh exclusive and was shown shown in early form at a Macworld keynote with Steve Jobs. The Mac did get Halo years later but no sequels to the first.
Bethesda - Oblivion, Skyrim, Fallout 3... How do I love thee?