There are many companies that share the "high end" stage with Mark Levinson. Halcro, Boulder, Krell, Meridian, MBL just to drop a few names.
What makes them so good? In simple terms, the sum of all their parts/design.
At this level of equipment, the buyer is looking for a level of performance that will sqeeze every note from a disc. The system should be able to play loud enough to sound live, without straining. Ear fatigue doesn't exsist, you don't have to listen for the music, it comes to you and sounds natural.
A Yamaha, Denon or other receiver offer people a way to have music and movies play back in their homes, at a price point that many can afford. They also know that the average consumer will be happy with the sound, as they usually don't know any better, or wouldn't be able to justify the cost differences.
Just as a Ford Focus or similar is perfectly fine as a way to get around, there are high performance cars out there that are built to offer a better, faster, more luxurious ride. They are built with better parts, better design. More things are done to ensure they are a better car.
High end audio does the same thing.
At this point it becomes a subjective topic.
Many people will claim they wouldn't be able to hear the difference from low end to high end, I think many are too scared of what they might hear, so they don't try.
A top end system can be like a glass of fine wine or a great cigar, it can arouse your senses and take you to that "other" place.