I respectfully disagree, perhaps not with your whole thesis but definitely your implication. Rock, punk, and metal can ramp up the anger and aggression like nothing else. However, I think most classical music is much better at representing things like beauty or joy. Of course "classical music" is a massive over-generalization, since one is compressing hundreds of years of music history into a genre. Personally, I love things like Bach fugues for their multi-voiced intricacy. Nothing I've found in modern music really scratches that same itch in me. I love other classical composers and pieces of music for different reasons. At the same time, I listen to stuff like Streetlight Manifesto or Machinae Supremacy or Mumford and Sons or the Les Miserables soundtrack (picking at random from what's currently on my phone) because of the emotions they create in me and the different sounds.
I think modern music is on the whole more heavy-handed with emotion than classical music. It tends to hammer your "anger" button or your "sexy" button or your "victory" button, etc. much harder and it pays for that with a lack of nuance in most cases. Take "Thunderstruck" for example. It is a pretty damn repetitive piece of music when you get down to it (solos aside). It basically just sits at "11", volume-wise and it has all of four chords. That isn't saying it isn't a good song or saying that it isn't successful at conveying the emotions it wants, just that power chords and sixteenth note arpeggios aren't everything.
Of course, we're comparing the best of nigh on 500 years of music with whatever we remember from the last 60-70, so classical music is naturally going to have a lot more positive examples. I personally think that they complement each other. The modern potential for intensity combined with classical technical expertise (there is a lot of classical piano that is at least as technically challenging as anything that any power metal band has whipped up) and the ability to back off and play pianissimo for part of a song makes for better music.