At least check out the last link if you're short on time.
As for your original question, Sampras. As good as he was, and apart from countless eye tests, Roddick is generally a notch below the likes of Pete, Goran, Ivo and Krajicek especially in % of unreturned serves. An interesting thing about this stat is that it usually corresponds with what one would expect from the mainstream consensus (for lack of a better term), which tells us that, wrong as it may be, conventional wisdom isn't entirely without merit.
Also there are other relative shorties whose serves have been nominated as among the best ever. McEnroe and Tanner come to mind, and Curren is another name that pops up in some (if admittedly cliquish) discussions.
And now's a good time to promote the greatest thread in TTW history: