This is hard as hell for me since I'm such a big fan of so many genres and on so many different systems. I could list 20 developers easily who I've had great times playing their games.
However when all is said and done there is one developer who has always delivered quality and I've spent more time playing their games probably more than any other. The great and fantastic
but honorable mentions would be
Square-Enix
Nintendo
Epic
Naughty Dog
Sucker Punch
Santa Monica
Microsoft 1st party
Ubisoft
and many, many, more