Last Christmas is one of Wham!'s most popular tracks but it only reached number one on the UK chart in 2021, some 36 years after its release.
Ridgeley, 61, reflected on the ongoing appeal of the hit while speaking to Vernon Kay on BBC Radio 2 show Tracks Of My Years.
After Kay said the song "typifies everything" he wants Christmas to be, Ridgeley said: "And I'm pretty sure George would be thrilled to pieces to hear you say that because that was his intention when he wrote it, to define Christmas in some way for people and it has come to do that.
"It is so evocative of an idea of Christmas.
"The keyboard part is reminiscent of sleigh bells, of course there are sleigh bells in it.
"Allied to the video which as you said represents an ideal Christmas, it has all the elements of cheer and so it has established itself as part of the fabric of Christmas.
"It's brilliance is that it evokes for people, Christmas, however that may be in their own mind.
"It covers so many aspects of a Christmas. You mentioned heartbreak, but love, yes."
Last Christmas was famously beaten to number one in 1984 by Band Aid's charity single Do They Know It's Christmas? which featured Michael, among a slew of other popular 1980s singers.
Asked if it feels like 40 years since the track's release, Ridgeley said: "Yes and no. It is a long time ago but hearing it and looking at it, it might have been yesterday. It hasn't dated."
He added: "I am extremely proud of the fact that my best chum wrote a Christmas song with the intention, set himself the challenge, the goal, of writing a perennial Christmas favourite and it has exceeded, I think, any scope of imagination with regard to its success in that respect."
Michael died on Christmas Day in 2016 at the age of 53.
Speaking about whether he listens to the song with a smile, Ridgeley said: "I do, I didn't for a year or two post his death, it was difficult listening to it."
He added: "But now it represents a joyful time, it's Christmas and also, in regard to our career together as Wham!, it represents really good times."
Earlier in the show, Ridgeley said the two, who met at school, bonded over their mutual love for the songs of Sir Elton John.
"Elton John, and particularly that album (Goodbye Yellow Brick Road) because it was fairly current to us both, was a stand-out and it was common ground so it was part of what bonded us together very early on, that shared love of music, that mutual appreciation of Elton John and that particular album", he said.
Kay said of the Tracks Of My Years interview: "It was really evident how much George Michael and Andrew Ridgeley loved each other.
"Their friendship was eternal and there's some emotional bits in his 10 track journey on Tracks Of My Years, and he talked about George so lovingly and you can tell that he misses George Michael an awful lot, like the rest of us."
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