Wimbledon, like the Rose Bowl, is still the "Grandaddy of them all."
When they make a bad tennis flick, they don't call it "Melbourne" or "Flushing Meadow."
If you were to ask any fan in the street to name a tennis tournament, odds are (outside of Paris, New York or Melbourne) that person will say Wimbledon.
And really, ironically, it's that outsider perception that counts. I think among hardcore tennis fans and the players, all the Grand Slams are equally precious because each of them is so different. The grinding, unforgiving cruelty of the red clay, the wacky bounces and tradition of Wimbledon, the crowds and jets at the US Open, the heat of Melbourne--there's a reason we make a big deal when a player gets a career slam, let alone a Grand Slam.
Of course, all of this goes out the window if Lena D. wins a slam, because obviously it woud automatically be the best.