These games should be free? ha! No. Regardless of how good/old they are, just because they have been available before doesn't mean some work didn't go into getting it into the store.
Especially the HD versions. These companies are not a charity. They are here to get paid and they charge what they think the product is worth. As a consumer, you pay what you think it is worth. If you don't think it's worth the asking, price, wait until it's down to the price you think it's worth or find cheaper means.
If you've already bought/own the game already, then you don't need to buy it again, these versions are for people who have never played it, used to play/own it but either lost their original copy or want to re own it for whatever reason.