I find the distinction "acoustic guitar solo" somewhat confusing and unsatisfying and the examples seem to be "acoustic taking the role of an electric in a rock setting". I'd certainly offer up a lot of traditional jazz as examples of fine solo guitar playing that does not require amplification or a particular "tone" to sound good and be intriguing. There's also a lot of good playing in classical and flamenco settings. Finally when you say "acoustic guitar" and ask me to pick something I'd like to listen to, I'd probably end up with Jorma Kaukonen. Like so many "best of" or "top" listings, it says at least as much about the compiler's experience and prejudices as it does about some kind of absolute, objective measurement.