Guns and Roses were a heavy metal group in the late 80's and early 90's, a period dominated by pop music. Paradise city itself may be seen as a hybridisation of pop and rock.
This image of the crowd flowing in further supports Fiske's theory; people are watching it because it is popular, likely to counter the hippie culture of the time. This also supports Hartley's theory that genres support ideological closure as it cements the gap between pop and heavy metal cultures, isolating them and preventing hybridisation.
This image was from a performance of the same song in the early 90's and supports Fiske's theory even further, the band are still popular half a decade later because people still like the music and what it represents. However, this also supports Hodge and Kress' theory that genres control the expectations of the audience, making it exceptionally difficult for the band to change it's type of music without losing it's audience and their credibility.
Her we see the older concert with a full house of fans, providing endless support for Fiske's generic conventions theory with it's clear popularity with the people. It can also, however, provide support for Hartley's theory hearkens back to the period when heavy metal and hippie culture were dominant and clashed over everything, making everything either hippie or metal.
I think that genres are ultimately defined by the people and control the behaviour of the producers as well as the audiences' expectations.