1987 "I Just Can't Stop Loving You" Michael Jackson with Siedah Garrett (1 week)
1987 "Bad" Michael Jackson (2 weeks)
1988 "The Way You Make Me Feel" Michael Jackson (1 week)
1988 "Man in the Mirror" Michael Jackson (2 weeks)
1988 "Dirty Diana" Michael Jackson (1 week)
2010 "California Gurls" Katy Perry featuring Snoop Dogg (6 weeks)
2010 "Teenage Dream" Katy Perry (2 weeks)
2010 "Firework" Katy Perry (4 weeks)
2011 "E.T." Katy Perry featuring Kanye West (5 weeks)
2011 "Last Friday Night (T.G.I.F.)" Katy Perry (2 weeks)
1988 is tied with 1989 for the second most #1 hits with 32 songs going to number one, and 1987 had 30 #1's, which are the years that Michael Jackson's five singles from Bad went #1. The Billboard rules at the time allowed a lot of different songs to go to #1, so it was a lot easier. Fast forward to the digital age, and now songs loom for much longer. So it is much harder to get a #1 since the top spots are always blocked by the same songs. There were only 17 #1's in 2010 and even less the next year, with only 14 #1's in 2011.
However, you could flip the argument and say that Michael's #1's were more impressive since Billboard's rules for charts at the time caused the positions to change very rapidly and therefore #1 hits were harder to maintain once they reached the top. In regards getting a #1 now, it is very unlikely that it will stay there for only one week, as most of them stay for more than two or three. So that would actually mean Katy's five #1's from Teenage Dream were less impressive.
What do you think?