I agree that Axl is what really made up the essence of GnR. His ego is what drove the whole ship. Not to say the others didn't step up when it came to time to massage Axl's ego with great albums.
But the other guys are a huge part. It's not like Axl was writin their parts. He was makin sure the album sounded just like he wanted.
Slash has one of the most recognizable sounds, and thats sayin somethin, since it's mostly real basic stuff.
Izzy gets overshadowed so much, but he wrote tons of riffs, and played the more lead-y parts on those riffs.
Duff just brought the attitude
The drummer for them was always replacable, as it was usually really basic stuff.