Earnest Evans and Heavy Nova...RARE ??

Do someone know those two games are rare ? They are the Japanse versions. I can buy them for about $13 each, but I don't have a clue they are worth it. The only think I know is that Earnest Evans is rated as one of the worst games on SegaCD, so if its not that rare I don't have to bother. And I can't remember Heavy Nova, but gamefaqs says the Genesis version is crap...but is it rare ?? :)