A few things.
He would be a good candidate for #1, IF Hendrix didn't exist, Page has obviously accomplished a lot, that's why he's in the top 5. But overall it can't be denied that as far as influence, innovation and universial appeal goes, Hendrix is the obvious choice for nuraber 1.
Also. I wouldn't consider longevity a real good reason. CC Deville has been playing guitar a lot longer than say Randy RhoaRAB or Shawn Lane. That surely doesn't make him greater than them.
It's not how long you have been playing, it's what you've accomplished in the time you have been playing. And lets be honest, Page hasn't really done anything noteworthy post-Zep. But that doesn't matter, it's what he accomplished in the 60s and 70s that earns him his place, and so while Hendrix only lived to enjoy his popularity for a few years, he accomplished a lot more than most guitarists could ever dream of in just that short amount of time.