That park bench scene is absolutely incredible and the entire movie is filled with great lines.
Personally, the best part about the movie was of course Mat and Robin's relationship but also Robin Williams' acting in it. We all know it but ever since he left, the industry lost a massive part of itself.
Dead Poets Society and Good Will Hunting are both phenomenal movies IMO.
The "perfect for each other" scene is one of the best in the entire movie too. Along with Chuckie giving Will a reality check.
Edit: A couple of people can't fathom the idea that watching a movie 15-20 years later you considered an incredible movie might not live up to those thoughts you first had. Let alone the fact that you appreciate certain movies differently depending on when you watch it in your life. How anyone can't grasp that is beyond me.