What makes a stamp collectible & desirable?

This has always intrigued me over the many years I have been collecting. I can reflect on what makes me go after a stamp & have always wondered if others do the same.

Primary for me, is whether I have the stamp and if I collect that country.
Second is the cost/value. There are many stamps that I would like to have and am missing, but they are out of my budget.
Third, is the appeal of the stamp. Is the stamp personal to me? Meaning, does the stamp have some relevance to me or my life.  Since I am Greek, stamps relating to Greece and it’s history and culture are of interest and I am prepared to actively pursue those stamps. But there are other driving factors such as historical importance.
High on my list is items from World War II, both the ETO & PCO (European Theatre of Operations & Pacific Theatre of Operations).

But there are many other historical events that I look for. One in particular, is the sinking of the RMS Titanic, which sank on the morning of April 15, 1912. Since I live in Canada, I look for used Canadian stamps with a cancellation date of April 15, 1912. This is no easy task. To date, I have not found any Canadian stamp with a recognizable cancel of April 15, 1912. They must be out there!

Here’s another historical date that I watch for: Oct. 29, 1929 . This date is known as Black Tuesday.
On October 29, 1929, the US stock market crashed in an event known as Black Tuesday. This began a chain of events that led to the Great Depression, a 10-year economic slump that affected all industrialized countries in the world.

While I have been searching for a Canadian Stamp with this date, I found one on the famous Bluenose (Sc#15 ), shown here.
As luck would have it, I was unable to purchase this stamp, as we had lost power for about4-5 hours in our area & had no internet access at all. By the time I was back on like, some other lucky collector grabbed this great stamp. My hunt continues!

Enjoy your collecting adventures whatever they are! Would love to know what others “hunt for”