I know there will be people chiming in saying "tone is in the hands, not the gear" blah, blah, blah. Is tone in the hands? Yeah, but gear is very important, too. I don't care what some people say, if Roy Buchannan played a bone stock Squire Telecaster into a SS Gorilla Practice amp, he'd sound like shit compared to Nancy into a Vibrolux. If he played a 1959 Les Paul into an original Marshall 100W Plexi, he'd still sound badass, but he WOULD sound different. A Lester into a Marshall sounds drastically different than a Telecaster into a BF Vibrolux Reverb. This said: What's more important?
I say amp. Give me a great amp and a decent guitar any day. An MIM Fender, Squire, Epiphone, etc... can be modded to sound pretty durn good. Plug that into a great amp, and you'll sound good IMO (IF you can play worth a rip in the first place). However, an original $200,000 1959 Les Paul plugged into a $50 Solid State amp (or any SS amp for that matter) won't sound inspiring at all.
To me, the amp is the more important piece of the puzzle.