I was amazed to see that James Pond 2: Robocod had been released on the DS. I played this game to death on the Amiga back in 1991. How can they justify the 20 quid price tag for a ported game over 15 years old? (even though I am tempted in the name of nostalgia ;-)
You've got it in one - nostalgia. It's a great way to make money, selling old games on new platforms.
They've done the same with Settlers 2 also on the DS.