Like Dan and Frank, my choice of collectibles is pretty much based on nostalgia. I agree with Cameron that the golden decade of bows was 59-69.
My collection consists of about 80 bows from Bear, Pearson Howatt, Hoyt, Wing, Browning, and Howard. I do have one or two Staghorns, Telums, Groves, Tice & Watts, etc...
Everyone collects based on what appeals to him. Don't discount the old Pearson bows. They are about the most under rated bows out there. When Bear and others were considered to be the best, but more expensicve, Pearson was making sound shooters at a more affordable price. They were massed produced about the same as Bears were. At that time, Fred Bear was more visible in his exploits. He probably did more to promote archery and bowhunting that any other single individual. In promoting the sport, he created a market for his company, and others.
When I was a teenager, I would drool over Archery Magazine and others, especially when I read the stories about Jack Howard, and seeing his ads for his GAMEMASTER. I never thought I would own one. Back in 1999 I learned that Jack was still making bows. I contacted him and bought a brand new GAMEMASTER JET. Over the next few years I became friends with him and managed to collect 8 of his bows, new and used. Sadly, he passed away about a month ago, so his bows will continue to be prized by me.
The real key to collecting is to figure out what YOU like, not other collectors, and go for it. The size of your collection, and what makes it up is up to you.
In my opinion, if you have two or more bows, you have a collection. Enjoy it.