guys who may have only played for a certain team for a brief period or other unique circumstances are typically where the value is. Older cards in great condition can be valuable but only if they come from series with limited runs or other special circumstances. Misprints in good condition can be valuable also. The biggest problem is that many people keep cards so there are lots of most players readily available. There needs to be something unique about the card beyond age for it to be valuable. I used to be big into sports collectibles but the market is not nearly as good now as it once was.