Sorry to be so biased but I find UK ads hilarious (British Airways are very clever and Hands off Humphrey (milk ads) are an old favorite), Japanese have some REALLY clever ones too.
I don't get into most of our ads tough, US or Canada, they are too tacky, not clever and definitely not very funny or engaging.
I find they are based on stupid jingles and ugly kids and show no real imagination, talent or creativity, much like most comedy movies these days.
So with that said: Here's ONE of my favorite ads for Cadbury, Phil Colins eat your heart out.
(Though this one isn't exactly the cerebral type of ad I was referring to, it certainly is one COOOOOOL gorilla!)
http://www.youtube.com/watch?v=TnzFRV1LwIo
turn it up!