If you're really interested in finding out what your cards are worth, don't just go by word of mouth, do yourself a favor and get yourself an issue of Beckett Hockey Monthly, or check it out on their website
www.beckett.com and find the hockey section.
All cards of every player have a different worth, so if you have a Gretzky rookie, you need to know what company made the card, and what condition it's in. Just like a card from a pack of MVP is worth less than the same player's card in a pack of SP Authentic, a Gretzky from a less desirable set is worth less. Also, graded cards are worth dramatically more if they in great condition.
I have thousands of cards, including about 700 red wings. I don't have many rookie cards, but I like insert cards which are harder to find in packs. I've got over 100 Gretzky's, over 50 Yzerman, and like 30 of Lemieux, Shanahan, Fedorov, Lidstrom, Osgood and other players I like or once liked.
I haven't bought any cards in years, but lots of them go up in value every year.