Lincoln's speech received a famously lukewarm to less than flattering reception in 1863, especially in contemporary newspaper accounts usually drawn along party lines. However even Republican newspapers don't seem to regard the speech as anything truly magnificent.
What were the circumstances that lead to the speech being universally regarded as great, and even quoted in other countries constitutions?
Part of It had a lot to do with the logistics that occurred after the speech was given. Normally, speeches were printed in full towards the back of newspapers, which is how most of the population came into contact with them.
The Gettysburg Address was so short, however, that newspapers were able to post it closer to the front if not directly on the front page. As you can imagine, that gave it a lot more exposure.