[TheOtherHobbes]

1st movement of Moonlight needs 5-7 years from a cold start to play well. You can learn to pick out the notes in less, but it's harder to play smoothly than it looks.

The 3rd movement of Moonlight is a Diploma level (i.e. university, 10 years of playing at a bare minimum) piece.

Guitar is popular because it's the opposite of piano. You can get somewhere recognisable within six months or so. But many players plateau after that. Really good guitar isn't any easier than really good piano.