I don't want to talk exclusively about bad commercials, so I do feel the need to throw in the occasional gem. The tough part about qualifying a commercial as "good" or "effective" is the fact that you have to notice it's good. Technically the best possible ad wouldn't be one where you'd think "Hey, good ad," rather, it would be one where you'd see it, and there wouldn't be time to think about how great the ad was because you'd already be driving to the store.
That said, sometimes the stars align and you get a commercial that you notice, love, and feel sold on something. In this case, it comes from the unlikeliest of places - automobile advertising:
Where's the corny exchange between husband and wife? Where's the full-throated announcer ready with clotted boilerplate about how anti-locking, all-wheel driving and streamlining this Cabrio is? How about the leasing info? And the indecipherable half-jokes, where did those go? This ad is stripped of the templated borefest that plagues the sad majority of car commercials. It's just arresting visuals, a beautiful soundtrack, and a simple, intuitive message ("Who wants to go to a party when driving in this car is so much fun?")
When this ad ran in 2000, everyone benefited. Young people were introduced to Nick Drake, Volkswagen saw its Cabrio product (now called Golf) continue to grow into the world's third best-selling car model, and automobile marketers got to see how it's done.
You don't hammer it home with slogans and taglines, you don't overwhelm with leasing information or yawn-inducing product attributes, and you don't make us cringe with hamfisted humor. You simply concentrate on one message, and you offer it in an engaging, artful way. Remember, marketers, we have brains - let us use them.