For me collecting lost a lot of its fun around 1990 when it just became a big market saturation and an investment thing. Lots of interesting innovations came along mind you but for me much of the joy and fun was destroyed. For the most part, my full set collection stopped not long after (like 94 or 95), which was kinda sad because I had been at it a few decades. That said, since 2000 there is one set I have actually tried to complete and I am still 7 cards short. They almost never surface. It's the 2003-04 Parkhurst Original 6 Toronto set. Not that it is anything spectacular, just a challenge. If I could ever finish it, it would be at most 1 of 20 complete sets, though possibly the only one, given there are many cards numbered to 20 or less.
Man oh man is it hard to get the last 7. Missing:
Sawchuk/20 Glove
Kennedy/20 glove
Conacher/20
Clark/30
Barilko/20
Sundin/50
Bailey/20 RN Glove