Why it still hits
You'd think a movie about a math genius written by two guys in their twenties would be a self-indulgent mess, but Good Will Hunting succeeds because it's actually a movie about fear. Will isn't a hero because he's smart; he's a protagonist because he's stuck.
For parents, the 'It's not your fault' scene is the emotional epicenter, but for a teen viewer, the most important character might actually be Chuckie (Ben Affleck). His realization that his best friend is 'sitting on a winning lottery ticket' and is too afraid to cash it is a powerful look at friendship and social mobility.
The 'Aged' Factor
Sometimes movies from 1997 feel like they were filmed in the Stone Age. Good Will Hunting avoids this by focusing on the 'Southie' culture, which was already a bit of a time capsule when it was filmed. The fashion is dated (so many baggy sweaters), but the psychological core is timeless. If your kid can get past the first ten minutes of 'wicked smaht' accents, they'll be hooked by the chemistry between Damon and Williams.
"You'll have bad times, but it'll always wake you up to the good stuff you weren't paying attention to."
This isn't just a movie for people who like math; it's a movie for people who are afraid of what they're capable of. It’s also one of the best ways to introduce a teenager to the idea that the adults in their lives are flawed, complicated people who have their own stuff to work through.