It all depends on what you collect. If you use logic and reasoning in investing you should always win more often than you loose. Why are old baseball cards highly collectible? Because back then kids bought them for the bubble gum and threw away the cards. Only the occasional kid would collect them and even then massive amounts where thrown away. But now people want these cards and there are very few of them even though a lot where produced. Newer baseball cards are printed in huge amounts and because old ones are valuable they are collecting the new ones thinking they will sell for more in the future. Maybe they will be hundreds of years from now, and only the cards kept in hard plastic under optimum conditions survived. But because so many are collecting now, they won't be worth much in the near future.
On the other hand beanie babies became a big bust. Why? People hoarding huge amounts of them thinking they where going to be worth some. The reprieved future value's where inflated because of "price guides" and although they where hot commodities at the time it was ONLY because of the inflated reprieved value. Much the same cam of the tulip. Anyone buying anything because of some preconceived notion that this "collectors edition" of an item will be worth something is fooling themselves. Items with words like "collectible" on them or items seen as possible collectible for future investment are likely to be hoarded and then sold in massive amounts at a later time (thus their value will go down). The only collectible toys that should be collected are those that are produced in extremely limited amounts. However toys that are seen as junk could very well be worth something if the condition is kept top notch. Because most of these toys will be played with and eventually thrown away. I remember seeing an old stretch toy go for thousands because it was shrink wrapped in hard plastic and kept it optimum temperatures (thus it didn't melt).
There isn't a 100% surefire way of knowing what will be highly collectible, but a little bit of reasoning can help increase your chances. Timing is key with investing into anything.