hi gorex, welcome.
about creating rock music with music geneator i would like to say this: in my humble opinion our beloved software is simply inadequate to simulate a good, realistic sound of a real guitar. it doesn't depend on your ability or experience. the guitar is probably the most complex instrument which a software can emulate, so it's not a matter of 'good combinations' of guitar string samples with the most appropriate effect.
as for the emulation of the real sound of the drums i think that music generator is pretty good, especially music 3000, which has very good samples that are not included in the previous games. for the kickdrum, i recommend gated and mid wet. for the snare i recommend chunky, splashy, rock hat. for the cymbals i recommend dribble, crrashed, classic crash, crashespect, megacym, rideithigh, rideitlow. the hihats are not that important, there are a lot which can be used. for the toms i recommend acoustic, big wet, dry, gate tom 2