But before GnR what rock and roll bands were any good (compared to rock in the 70s, and the alt/grunge movement in the 90s)?
as chaos mentioned above, maiden was around, but i would separate the metal scene from this discussion and metal, along with art rock, hardcore, and post-punk is definitely where the most interesting rock music was happening in the 80s. but even limiting ourselves to popular rock music (not getting into the aforementioned subgenres), i would include:
zz top. eliminator is the only good album they released in the 80s, but it is a fantastic album even if somehow reviled by music snobs.
ac/dc. back in black. for those about to rock. it's not bon scott, but it definitely rocks.
springsteen. the river is amazing and born in the usa is a great record. if not for the era-specific production on usa, it would be a stone cold classic.
U2. bono is about as insufferable as a human being can get and a lot of the later stuff is horrid, but up through joshua tree they were amazing.
the police. okay sting might be as insufferable as bono. but still, even if you only listen to stewart copeland, those records are fantastic.
van halen. yes, their debut is their best album, but women and children, fair warning, and 1984 are all fantastic. fuck van hagar, though.
aerosmith. personally i don't like anything they released after rocks, but many do and they're a fair inclusion imo.
if we actually did include subgenres, this list would go on forever. hardcore and metal were exploding and the best bands of both genres were releasing all their best stuff in the early 80s.
If you are using Tom Petty as an example of the awesomeness of 80s music, well that's just wrong. Not that Petty is bad, mind you, but if he is the best the decade has to offer it was a pretty weak decade.
petty's best music came out in the 70s and 90s and he was still among the top five rock artists working in the 80s. there's a reason he was chosen by bob dylan, george harrison, roy orbison, and jeff lynne to accompany them in the traveling wilburys.