I agree - the Apple logo is a great iconic symbol. Apple has always been about clean design and this logo's initial examples in silhouette, color, gray scale and 3D metallic prove the point.

However, it also took a series of great products with a consistent design philosophy and well defined brand image to make the logo resonate so successfully.

The Apple Computer logo was originally criticized for being very similar to the Beatles' Apple Corps logo - a Green Apple - many considered that logo iconic as well, but it has faded in time with the ubiquity of the Apple Computer design.

Interestingly, The Beatles Apple logo was derivative itself - borrowing the Apple from the famous Magritte painting that I believe was purchased by Paul McCartney.

Here is a link to some of the storied Apple Corps v. Apple Computer litigation and an example of the Apple Corps logo: http://j.mp/bw326f