Well you could probably remove your iTunes library.xml file in your documents folder, but that would require you to add all your music again to iTunes, and when you sync your iPod it'll go through copying everything again, etc.
I suggest you create a new smart playlist (that's all they are, anyway), by going file->new smart playlist, and telling it to find the top rated ones (such as all the 5* ones), or the ones added in the past 7 days, or whatever.