Beethoven expressed power not fustration.
EMO expressed lonliness and anger.
I think Beethoven was more frustrated with not being appreciated. He does get emotional, and is sometimes called Romantic though he's in Classical Era. I'm not sure, but doesn't Sonata Pathetique express a battle with frustration?
"The second theme (of 1st mvt) is warmer and more nearly approaches the lyric vein... strikingly suggestive of the mood so common to young but gifted souls, in the bitterness of their first pained surprise at the cruel contrast between the ideal and the actual in life..." - Perry, Descriptive Analyses of Piano Works
There is so much more to emo, but I doubt the people here know about that.
First off, what is commonly termed "emo" is a misnomer. The real emo genre and sound came years before what is now mistakenly called emo.
From Mineral (what can be called a POST-EMO band) - Gloria:
A brave morning
thoughts flap their wings and fly
and I can still taste
defeat on my lips
Bright tie, fish fly
I have not yet arrived
How can I not admit
I need to know you?
'Cause I just want to be
something more than the mud in your eyes
I want to be
the clay in your hands
Hey sorrow,
where are you?
Tomorrow just won't be the same
without you here
I wish for shoulders
bold and broad to bear
and strength to
hold my head above them
'Cause I just want to be
something more than the mud in your eyes
I want to be
the clay in your hands
Gloria is silent... and glory is a silent thing.