The latest one that took my breath away and could classify as a short film itself for its storytelling is the West End's Miss Saigon trailer, though I don't think it ever aired on TV as a commercial:
There is also the original Pippin commercial which is pretty great. And then a rather bizarre commercial from the cast of Cats encouraging humans not to smoke.
I remember seeing the commercial for Ain't Broadway Grand many times (I was in college in NYC at the time). I don't really remember the visuals, but the music sounded like it was being played on a Casio keyboard. Definitely the worst commercial I've seen. :)
I was just watching the news on ABC and saw a new commercial for Tootsie that was pure cringe. The commercial just features several people laughing uncontrollably in front of a background (I think it's red with review quotes or something). We are obviously supposed to assume these people are audience members, but the laughter is so fake and forced it just comes across as embarrassing.
On the other end of the spectrum they also showed a commercial for Cursed Child that really makes me want to see the show.