Personal Note: Because only one couple was chosen to represent each year, many classic pairings were left out (while some pairings wouldn't even be considered to be 'classic'). Especially surprised that the successful pairing of Michael Tao/Kenix Kwok in the "Detective Investigation Files" franchise was excluded (from the title of this poll, I automatically thought of them; they are also my favourite pairing of all time); don't know why the pairing of Gallen Lo/Kathy Chow in "Plain Love" was selected instead.
Also surprised about the exclusions of Damian Lau/Liza Wang, Felix Wong/Barbara Yung, Gallen Lo/Maggie Cheung, Bowie Lam/Flora Chan, Louis Koo/Jessica Hsuan (their pairing in "Detective", in particular, was definitely more well-liked than Tim and Helen in "A Threshold of an Era"), and Julian Cheung/Charmaine Sheh.
Although "Square Pegs" was aired on December 30th, 2002, the majority of the series was aired in 2003, so it would make more sense for Ah Wong and Choi Fung to represent 2003. When "Triumph in the Skies" aired, the Sam-Belle and Vincent-Belle pairings were definitely more well-received than Sam-Zoe....
Many of my favourite (and definitely deemed to be classic) couples are already out of the running, but I guess I can still vote for Bobby Au Yeung/Esther Kwan and Lawrence Ng/Ada Choi. ;)
*Credits to myoliewu.org and HKLOVE.org