its your tone.

classic bands like GnR put a stress on a good tone.

they used tube amps, nice guitars, and some effects on top of that to get a sound that they really liked.

...it'll be impossible for you to get that EXACT sound with what you have.
for sweet child of mine, you need effects like reverb, overdrive, chorus, and a slight delay. if you play with your settings on your amp, you could get somewhat close to the distortionish sound, but it wont sound as good as on the album by a long shot.