Honestly I can say that every era of Batman is my favourite purely because every era has contributed (great or purely entertaining stories) to the chameleonic appeal of our favourite character.
Growing up I assumed that, until Denny came unto the scene in the late 60s, nearly every single Batman story since Robin's 1st appearance was completely caked in camp and, typical of comics in those days, lacking in any character development. And then from the 50s-early 60s (the era of space aliens and planets and coloured Batman costumes) I discover 'Robin Dies At Dawn' a moving portrayal of Batman's fear of loneliness and failure decades before it became a recurring character norm.
As fans we all have certain tones of stories (those who grew up with a Batman who was a pure hero will prefer the, relatively, lighter stories and those who came to Bats in the late 80s will prefer the darker take) but personally I've found genuine value in something of every era.