Lists of "Greatness"

People often make lists of "great" blank, be in movies, songs, politicians, etc. However, what makes something great? Today I read a list of the 50 greatest movie soundtracks (http://observer.guardian.co.uk/omm/story/0,,2032992,00.html). Now, I like a good soundtrack, but I haven't heard of half of these movies. Why exactly are they so great?

There are a few ways to define greatness. One is just subjective, I like something therefore it is a great. Another is by popularity, though not in the usual sense. The list has The Wizard of Oz in the number 1 spot. I agree with that choice. Who doesn't know "Over the Rainbow?" Thus, it is great because it is timeless, a part of pop culture over 70 years later. A third way to define greatness is by some technical measure. When discussing greatest sci-fi movies, Star Wars Episode IV has to come in near the top simply because of the technological breakthroughs in creating it.

One issue I have with "great" lists is that often they discount in some way. For example, in this list, a John Williams score is listed only once. But think about it. Go to a piano and play the low, menacing shark theme from Jaws and see who says, "What is that?" Likewise, the Harry Potter and Indiana Jones themes are known by almost everybody. (Real greatness is when a movie is remade or has a prequel from a completely different writer and director and they use the original theme song as Shaft and Superman Returns.) Even if a score is by the same composer doesn't mean it can't be greater than another score on the list.

Overall, greatness is really subjective. But wouldn't it be nice to see a list of great soundtracks actually have soundtracks that people know and understand intuitively are great?