Pokemon, and it's not even close. As far as I know, Duke Nukem is really only notable for introducing some more risque aspects to video gaming, but that hardly makes up for the fact that Gen 2 pokemon games are just vastly superior in every other way.
Pokemon Gold/Silver/Crystal built on the success of the original pokemon series. True, it's easier to build on genius than to create it, but generation 2 games really are what perfected the series. The good folks at Nintnedo set the precedent of adding new pokemon, new starters, new legendaries, new gyms, new Elite 4, new lands to explore, new everything. Unlike the other games though, they changed just enough, and not too much.
Pokemon takes this one. I think it can do some serious damage in the tourney.