Letterman and Leno were up for the "Tonight" show emcee job when then-host Johnny Carson retired 22 years ago.
Leno ultimately got the job and has consistently beat Letterman in the ratings since.
NBC announced Wednesday it is replacing Leno with Jimmy Fallon as "Tonight Show" host, in hopes of appealing to a younger demographic.
In response, Letterman read a list of "Top 10 Things We Will Miss About Jay Leno" on Wednesday night's show. It went as follows --
10. Whenever he used a "Headline" I sent in, I got a "Tonight Show" T-shirt.
9. Now I'm the only guy in late-night television who's not a Jimmy.
8. He looks damn good in denim.
7. Driving one of his antique fire trucks.
6. Playful spats with ['Live! with Kelly and Michael' producer Michael] Gelman.
5. If you broke down on the freeway, Jay was always there to help with a camera crew.
4. Can't remember the name of the bit, but it's the one where Jay is walking.
3. He's Mom's favorite talk show host.
2. I won't be able to do this anymore (Dave does Leno impression.)
1. Watching him interview big stars who won't do this show.