Exactly what I was going to say, particularly the last part. I sold over 100+ Saturn games in 2006. Made quite a nice buck. I sold off those games which I knew I bought largely for collector's reasons. I didn't really need SF Alpha 1 when I had SF Alpha 2.
Just sell out those games you know you wouldn't miss. Hang on to the rest, and if you still feel the same way in 6 months, start the weeding out process even further.