When dealing with music genres that have their own associated subculture, you have to go beyond analysing the music and understand the context of how emo emerged.
Emo, in short, came about as a response to hardcore punk. Where hardcore punk music was driven by aggression/anger, emo music was driven more by personal emotion. Which is why when people ask me what emo is, I say emo is (was) like punk rock, but more "in touch with your feelings".
This all reminds me of how that whole "alternative" movement took over MTV in the 1990s. Back then everything on modern rock radio was considered "alternative". But that whole age of alternative music came about with the rise and demise of Nirvana and grunge music, which was itself a response to the frivolous glam rock/hair metal of the 80s. By the mid 1990s the whole concept of alternative music being the alternative to whatevers on mainstream radio was already lost.
UK punk rock in the 70s, rock and roll in the 60s and blues music sung by slaves in pre-emancipation America.
All these "genres" came about as a response to circumstances of the times musicians were living in and original context of their music gets lost as the world moves on. Especially when music has become more of a consumption good than a form of art.
It's all about context.
and as for purely emo, u may try hearing bright eyes, elliot smith... usually emo sounds very mellow and sad...just an info for you... 
