Best male tennis server ever

[Actual God]

Debate: Who has the best serve ever?

Three friends. One says "I can't believe Federer can break Roddick so much - Roddick is the best server ever."

The two other friends object. Friend number two is like, "No, Pete Sampras is definitely the best server ever."

Friend number three says, "Maybe he had the best service game, but he's not the best server."

What's the answer? I'd say Goran Ivanisevic, but that might be a little too first-serve-only-when-it-goes-in weighted. Also I don't know much about tennis.