First off, a little disclaimer to anyone who's thinking about taking the topic in this direction.
This is NOT a discussion about how easy/hard legendaries are to get.
This is NOT a discussion on the requirements of obtaining legendaries, whether it be by drop rate or quest completion rate.
This is NOT a discussion designed to bash specific legendaries.
This IS a discussion on the central lore, mechanics and themes of legendaries.
Since classic and every expansion onwards, there has been more than one legendary to obtain during the course of that period. Upon reflection of these legendaries it is safe to say that they can be split into two slightly blurry but still easily distinguishable categories.
1. The Lore Legend: This style of legendary is basically a player-obtainable version of a very important item that iconic heroes have once possessed. A very obvious example would be the Twin Blades of Azzinoth and Atiesh. These were very commonly seen until halfway through WotLK, with Val'anyr arguably being the last style of legendary in this chain.
2. The Crafted Legend: This style of legendary centers around the idea of creating it as events unfold. The most famous example would be Shadowmourne and the recent legendary cloaks. Since ICC this has been the main style of legendaries as most if not all of them are based around the idea of heroes creating a weapon or tool powerful enough to defeat a great evil.
So I ask this: Out of these two choices, what is your personal favourite style of legendary? For me, it's The Crafted Legend. The idea of progressing the story and having new legends born out of that progression is much much more satisfying than clinging on to old, established examples.