The lack of Portugal in the game makes perfect sense. The 4 powers chosen all had a serious stake in the new world because they were all trying to figure out a way to get AROUND it to get to the Indian Ocean. The Spanish, French, English, and Dutch really could have cared less for this New World initially; it was just a big obstacle of land getting in the way of where the known wealth in the world was concentrated.
Right before Columbus made his famous 1492 journey, Portugal's Diaz and DiGama had found a way around Africa's southern tip, which allowed them access to the Indian Ocean and all its wealth, without having to cross the vast deserts, stretches of land, and bandits. The Pope, in order to preserve the peace between powers, gave Portugal a monopoly on the South-African trade route, and none of the other powers of Europe were allowed to use it. In fact, this is the exact reason that Columbus sailed for Spain, and not Portugal. Columbus didn't sail to prove the world was round, he sailed because Spain wanted a route to the wealth Portugal had managed to find, and had some spare troops left over from the Reconquista that needed a distraction.
Thus, Portugal had zero need or desire to try and find a western trans-Atlantic route to India, because they'd already found one to the south. So while the rest of Europe was fumbling around the new world, setting up waypoints, and searching the land for some kind of quick access to India, Portugal was content to leave the rest of them to waste their money in the new world while it made Bank in the Indian Ocean.
It wasn't until Cabral "got blown off course" to the eastern shores of Brazil that Portugal really played any -direct- role. Their INDIRECT contributions, such as Portolan Maps, and the Caravel, and Henry's School of Navigation were invaluable assets used to find and explore the new world, but their direct involvement was not until much much later, after the other four powers realized there was wealth and power to be had from the New World, that they couldn't get to India because the New World was too dang big, and decided to colonize to the point that they were well established and had control over most of the New World.