Let's stick just with the #1 songs on the Billboard Hot 100, to make sure we're talking about songs that were popular. Also, here are the criteria for counting a song as boy-crazy, as above a mere love song:
- Expresses song kind of yearning for the guy (whether unrequited, celebration of current love, or a torch song, doesn't matter).
- Singer can't help the way she feels: it's involuntary, won't go away even if she wishes it could, and in general lacks control over her feelings. This must hold for both the lyrics as well as the emotional expression in her voice.
- Some sense that if she doesn't get him, she'll explode or wither away.
They don't start until about 1960, about the time the crime rate started climbing. And clearly 1989 was still chock full of these songs, and had the last of the great ones -- "Like a Prayer." By going to the bottom of the previous link, you can navigate around the #1s from various years. Just eye-balling it, I see a sharp drop-off even beginning in 1990. Remembering that social trust levels fall before the crime rate falls, it looks like boy-craziness is more driven by how much girls trust boys, and less by the crime rate per se, which peaked later in 1992 (except to the extent that these are closely related). Still, that's just from eye-balling; I don't know a good number of the songs, so I'd want to get more quantitative before settling on that conclusion.
There's "I Will Always Love You" in 1992, I guess. No later than 1997 the counter-revolution against boy-craziness had triumphed, as shown by the chart-topping "Wannabe" (that annoying song by the Spice Girls). It's an anthem for emotionally in-control, cold-blooded, pushy, laundry-list-scribbling harpies. That's something else to bear in mind when we look at the trend -- not just adding up all the boy-crazy songs, but subtracting points for ewww-boys-yucky-shoo songs like that one, or vain and emotionally dead ones like "London Bridge" by Fergie.
In 1999, we got "...Baby One More Time," not a very danceable song like the earlier ones were, but still something that could've been a late '80s head-over-heels radio hit. That looks like the last one. "Genie in a Bottle" by Christina Aguilera falls short because it's too much in the Spice Girls direction of, well, bottling up her emotions and issuing a vague list of do's and don'ts to potential suitors. Beyonce's song "Crazy in Love" looks like one on paper, but it doesn't make the cut because she's faking it on the vocals; she doesn't sound hopeless. Same with "Promiscuous" by Nelly Furtado, whose voice sounds more mercenary. And Katy Perry's voice is hollow no matter what she's singing about.
While it's clear that there was a die-off around the early '90s or just after, what about isolated cases since Britney Spears' 1999 hit? Some of those didn't ring a bell, and I don't feel like YouTubing them all right now. Again, just looking at #1s on the Hot 100, to make the same comparison across time.