If you're of the mind that us young whippersnappers' music all sounds the same, it turns out the science backs you up. The younger generation may have some great new ways to listen to music, but it seems kind of pointless if it all sounds the same.
There exists an archive called the Million Song Dataset, which proves art can be looked at somewhat objectively. It breaks lyrical and audio content into data, and it covers pop songs from 1955 to 2010.
Researchers in Spain ran all this data through a few algorithms and found that pop songs, over time, have become generally louder and less complex (in chord progressions, melodies and the types of sounds).
The latter two might be obvious (though, less variety of sound? Lil' Wayne uses a freaking fire siren as an instrument all the darn time).
Loudness is a little more confusing. When a song recorded, it's recorded at a certain volume. That volume determines a baseline for the song when it's played through your speakers. If you've ever been calmly listening to your iPod at mid-volume and had a song come on and blast your ears, you know what I mean.
Why they're doing this wasn't studied, but we can proffer a couple of pretty obvious guesses. The louder a song is, the less a listener might notice those complexities. Plus, it makes itself known.
Nonetheless, if you get bored, feel free to compare a song from The Temptations to one by Katy Perry. I bet this study won't be that shocking.