The closest thing I can think of is,
"The grass is always greener on the other side of the hill"
or perhaps,
"You always want what you don't have."
Neither really conveys the meaning of the original though. The other mention of this phrase is on a blog of someone who seems to like cars, so it would be appropriate for someone who's nostalgic for old classics and drooling over modern sports cars.
Searching for that phrase on Google only turns up 3 matches: this page, and two blog entries from someone named Ken. Maybe he, or someone else coined it recently, as diceke said.