Being a skeptic, cynic and contrarian, I didn't trust or accept the notion that The Beatles or Stones were the best, so I explored deeply and obsessively only to find out that for my taste that title should go to Phish and then backwards down the number line to various other artists who may or may not fully align with the rock classification but who appeal to me.
Delving into jazz is a bit different too, because you are instantly going to encounter Miles Davis and then it's pretty much downhill from there. Almost without argument it's easy to see how he is the best ever to define, conform, refine and expand that style of music. And yet, no one could have told me that I would develop a slight preference toward Sun Ra's eccentric and prolific output over Miles' more tailored approach.
One thing about classical music that can be confusing is do you seek out the composer, who may have died so long ago that there aren't any actual recordings of him or her playing his or her own music, or do you seek out the group/performer (AKA symphony, AKA orchestra, AKA ensemble, AKA violinist, AKA cellist, et cetera) and focus on their recordings/performances?
Rather than star with Mozart, Beethoven or Bach, I'm assuming that I'd like to start contemporary* and then work back (or forward) from there. I haven't exactly found my Phish or Sun Ra of the classical world yet, but I'm still looking. Suggestions are welcome. Maybe I'll discover that more mainstream movie soundtrack composers like John Williams, Alfred Newman or Ennio Morricone are where it's at.
*None those composers or classical musicians I namechecked above are what you would call new, even the modern ones. By contrast, in the rock world and even the jazz world I'm aware of artists under 40 who are making great music. Is there a relatively new composer and/or classical music ensemble offering a vast reward to those who find them?