That reminds me. Awhile back, when I had my GH100L, I did some back to back clips. One was of my Mark III and the other was of my GH100L. I was able to get both to sound almost the same (the GH100L was being boosted where as the III was straight in.). Random Hero can attest to this as I showed him the clips. Unfortunately, I no longer have them on my computer. I told this to Mega recently and he claimed there was no way they sounded the same in the room. To me, the difference was the exactly like Ed said...in the feel.
I can get most amps to sound the way I want them to, but it's the feel and how they respond that turns me on/off an amp. When I play through someone else's rig, I sound just like me. I don't sound like the other guitarist at all. To me, that's proof most of the tone comes from how the individual dials in an amp and the individual's own playing style more-so than the actual tone of the amplifier.