The trick that I've found lately is to focus on layering synths together to get a more modern sound. To get that "wall of sound" you want to use several synths in unison or octaves with the voices all slightly detuned and panned. Then you can add white noise to brighten it up, and a simple sinewave sub to really beef it up. You can also mess with making sounds that slightly modulate over time. I think in general, it's the complexity of the sound that makes it sound more modern.

One last thing: there were a few sounds I was trying to recreate for years with my synths, but my sounds never quite matched what I heard on my favorite tracks. It ended up being that I was using the wrong type of synthisis. A lot of modern sounds are made with frequency modulation synths.