Both are among the biggest rock acts in history, so it's hard to say
Guns N' Roses
Guns N' Roses
Guns N' Roses
Guns N' Roses
In America, Guns N' Roses are more popular; but internationally, it's a tie.
Matter of opinion
Led Zeppelin
Led Zeppelin
In general, Led Zeppelin is more popular than U2. Yes, U2 has been probably the biggest band in the world since the 1980s; but Zeppelin still sold more records than U2 did, so Zeppelin's the answer.
adele
Led zeppelin, who sold the 2nd most albums of all time
As i am not a musician but gnr sounds much better than motley crue.