I really don’t know (I don't have these games) but I know one Nintendo games website that I usually buy from and they have a huge selection of Nintendo games, I’m pretty sure you can find these games there for about 15$ a pop.
Pretty much what everyone has said. If the games are fun for you and have good replay value and won't be paperweights after you beat them, then 40 for those games is a good value. But if you don't play them often or give up on them for good or something, then it wasn't a good deal.
I have had a chance to play these games and I have come to the conclusion that I really like contra four so I am very happy that I bought that. But Space invaders extreme doesn't have much replay value. I think i'm gonna trade my space invaders extreme on Gametz.com.
Overall I'm glad I did the deal because of me getting contra 4.