I guess you had to be there

What you say when someone tells you something he thinks is hilarious but really isn't. You say this to avoid hurting your friend's feelings in breaking it to him that his joke sucks.

Dudeman 1: "Oh man, I was playing horseshoes in Red Dead Redemption and I got a really close throw and John was all like, 'Did you see that!' It was so funny dude!"

Dudeman 2: "I guess you had to be there."

Dudeman 1: :(