Well bearing in mind that the Exorcist was made in the early 70's, I think it's aged remarkably well.
Some of the lines are a bit corny. But i remember going to see it on the Big Screen in the late 1990's (when it was re-released). The cinema was packed, and the audience were soon laughing at the outdated dialogue.
But believe me, when the movie got going, and the exorcism began in earnest, you could hear a pin drop in that theatre. The tension was palpable.
It takes a very good movie to have that effect, even today.