The best poetry is what we want; the best poetry will be found to have a power of forming, sustaining, and delighting us, as nothing else can.

Everything depends on the reality of a poet’s classic character. If he is a dubious classic, let us sift him; if he is a false classic, let us explode him. But if he is a real classic, if his work belongs to the class of the very best (for this is the true and right meaning of the word classic, classical), then the great thing for us is to feel and enjoy his work as deeply as ever we can, and to appreciate the wide difference between it and all work which has not the same high character. This is what is salutary, this is what is formative; this is the great benefit to be got from the study of poetry. Everything which interferes with it, which hinders it, is injurious. True, we must read our classic with open eyes, and not with eyes blinded with superstition; we must perceive when his work comes short, when it drops out of the class of the very best, and we must rate it, in such cases, at its proper value.

And yet Chaucer is not one of the great classics. His poetry transcends and effaces, easily and without effort, all the romance-poetry of Catholic Christendom; it transcends and effaces all the English poetry contemporary with it, it transcends and effaces all the English poetry subsequent to it down to the age of Elizabeth. Of such avail is poetic truth of substance, in its natural and necessary union with poetic truth of style. And yet, I say, Chaucer is not one of the great classics. He has not their accent. What is wanting to him is suggested by the mere mention of the name of the first great classic of Christendom, the immortal poet who died eighty years before Chaucer,—Dante. The accent of such verse as

‘In la sua volontade è nostra pace…’

Without poetry, our science will appear incomplete; and most of what now passes with us for religion and philosophy will be replaced by poetry”.

I just picked a few key things out from Mathew Arnold's Study of Poetry that I thought were important and down to the point. What I basically got from Arnold is that poetry should be beautiful and be meant to delight us and transcend us. But its damned hard to be a good poet and match his standards. He is pretty picky about who can be counted as one of the classic poets and not even Chaucer can meet them. And eventually everything will be replaced by poetry.
It was really long and kind of drawn out but I thought for the most part it was rather intelligent and even pretty. But I don't think many people could meet his standards.