In reply to Gordon Stainforth:
Nah, I hear what you're saying but I still think Gimme Shelter has a better intro than Satisfaction.
What the rest of the world recognise or not has never been of much interest to me in choosing music to listen to, recognisability was a requirement but the OP did ask for best intro ever.
In the absence of a correct answer being available, we'll have to agree to disagree I'm afraid.