One day a few years ago, Wendy and I were at a family function with Wendy's then 8-year-old niece, Sabryna.  Sabryna, like any kid, was playing outside and got something in her hair.  Here's the conversation that transpired: 

Wendy:  Hey Sabryna, you have something in your hair.
Sabryna:  That's ok.  I'm better than you.
The End

That was a life-changing experience for me.  What better comeback is there than "I'm better than you"?  It wasn't so much a comeback as just a general statement.  A fact.  "I like your shirt."  That's ok.  I'm better than you.  "Do you want something to eat?"  Nope.  I'm better than you.  "How was school today?"  Better than you.

In a strikingly similar instance, my friend Bob once went to a bar and had the following exchange with the waiter: 

Bob:  Hey, how's it going?
Waiter:  Better than you.

To this day, Bob still brings this up as a major turning point in his life.  How could a waiter say that?  How does he know he's better?  It's angering, dumbfounding, frustrating, and confusing.  Which is why it works so well in so many conversations.