This game is like Tropico, if you played, or something simillar to SimCity, but less complicated :)
I think this is an overly simplistic comparison... and not very accurate.
The main focus of Port Royale is the trading between the cities of the caribbean, while the city-building part is an afterthough.
In contrast, the main focus of Tropico is to develop your island. If I recall correctly, there was no advanced trading option between neighbouring nations.
It also doesn't exactly match settings. Tropico is set in the caribbean, true, but in the middle of the 20th Century, while Port Royale 2 is more like 17th Century.
Finally, and most important: One of the high-points of Tropico was the witty humor that permeated the game, and we all have to admit that Tropico would not be half as successfull if it was void of it. In contrast, the characters in Port Royale 2 are as flat and uncharacteristic as they can be, and the game is, if not serious, at least absolutely neutral on that point.
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Having that said, and in response to the OP question, Port Royale is a trade simulator, the kind of you can spend an hour or a hundred, depending of your tastes. The game can be a bit unintuitive sometimes, but does a good job of guiding you through the ropes, and the curve of difficulty scales fairly well. Most people think the lower point are the fighting mini-games, which aren't as fleshed out as they should be and they can be viewed as a "Sid Meyer's Pirates" afterthough/blatant copy/hommage.