From my experience of trying to learn several instruments I would rate lead guitar the hardest, saxophone close second, and either keyboards or bass the easiest.
i play the violin, bass, lead, piano, etc but the hardest is the bass because you do not exist unless you miss beat.
I'd say the drums as it is the only intrament that both hands and feet are used un-simultaneously
No idea but I would find saxaphone or drums hardest
I've played keyboard and sax. I'll say (from easiest to hardest): keyboards, saxaphone, lead gutair/bass gutair, drums. Drums is hard for me because I have a poor sense of rhythem.
these are all difficult and take skill and time to master. i dont know what id do if people stoppedlearnign these things and solely used computers to make music, theyre great tandomly but when the world is full of guitar hero who cant jam and musicians who cant play guitar hero we've got a problem.