In theory however, you cannot argue that an Amp modeler should be the way to go...
the half an instrument thing is pretty dead on i think, but think about it, your guitar signal goes into whatever amp, it goes through a variety of circuitry and then it gets blasted out via a diaphragm in the cabinet... then it is up to where you are standing in the room, and the room itself to produce the final sound-product that you hear.
everything in that step is calculable with mathematics, meaning it can be recreated because you can very easily emulate the circuitry of an amplifying, perhaps calculating the way it sounds coming out of the given speaker's diaphragm is difficult, but time will solve that..
Take the following diagram:
Riff x -> Guitar x -> (Amp x) -> Speaker x -> eardrum
Riff x -> Guitar x -> (Modeler imitating Amp x) - > Speaker x -> eardrum
If you did that, I am positive it would sound the same. Because we are only dealing with a signal electrical signal, given the proper schematics of the amplifier, there should be nothing holding back mathematical calculations from perfectly recreating that amplifiers coloration of the sound.
the problem is emulating the speaker and its interaction with the room and the mic, those things will be more difficult to emulate, but I think current modelers do a good job..
this whole thing is way to subjective though, personally, what i consider to be a "good" tone is one that acheive its purpose. I think a big part of the problem is that everyone is attached to these analog sounds that they get from certain combinations of antiquated equiptment.. its like a sentimental thing...
I personally find the advantages of digital guitar recording to be FAAAAR superior to the apparent tonal advantages of micing speakers...
basically, listen for something that sounds good, and DONT compare it to other guitar sounds... just listen to it for what it is and see if it sounds good.
if my guitar tone doesnt sound like any guitar on the planet, who gives a shit?? as long as it sounds GOOD as a sound, not an instrument!
