I really, really appreciate how John Petrucci plays guitar. There are many aspects of what he does, that I'd love to be able to do: Play very articulately, create wonderful, haunting even, melodies within a certain chord structure, and just fucking blaze when he wants to.
If I had ever gotten serious about creating my own music, he'd be where I would start. But then I'd also want to take all my other influences, mix them up, while also mixing in things of my own doing, and be able to come up with a unique-enough style of my own, that when someone heard me, they'd know it was me.
Put me in the camp of, "Why would anyone strive to sound exactly like another guitarist?"
Edit: Unless you're in a tribute band, like iaresee said.