Interesting question tbh!
Rush have undergone a few musical style changes over the years, but my favs are Fly By Night, 2112, Moving Pictures & Grace Under Pressure.
Personal fav is 2112. It has everything, the epic 2112 itself made up of several segments taking up all of side1 (showing my age!) & side 2 has the stunning ballad Tears along with some classic 3minute rock tunes.
In this age of Youtube I'd just say go and search for the complete albums, give them a listen and go from there!