Tropico is one of those rare games that can be as simple or as complex as you want it to be, and it ends up being fun on every level because of that. Even though it lacks a strong 'story-based' campaign, which I would have liked,
Tropico serves up more fun in a few hours than most recent sims do the entire time you play them.
Which is sort of surprising, considering the setting: you are a recently-instated Presidente of the little island of Tropico, and it's your job to bring the island from its current unsophisticated state to a place that you can be proud of. Definitely one of the most unique game concepts, Tropico puts you at the head of a banana republic and has you controlling almost every aspect of the island--culture, industry, housing, military, and so on.
One important thing to note is that you don't control your citizens directly; you can merely build places of work, set wages, and hope that people come to them. Every citizen of Tropico has a mind of their own, and it's patently impossible to appease everyone. Instead, you've got to try to make the most people happy as you can, by providing the services and lifestyles that they want.
As with any good, complex game, Tropico doesn't make this easy. There are a number of factions in the game--militarists, intellectuals, environmentalists, and so on--and everyone belongs to at least one of the factions, to some degree. Of course, when you make a certain faction happy (by, say, making the loggers cut only half of the trees they usually do, to keep the island beautiful), you usually end up pissing off another faction (the capitalists aren't too happy with this blatant disregard for maximizing profit). These sorts of checks and balances require a lot of fine-tuning, and you'll still be finding subtleties in the engine many hours into the game.
There's also a complex political engine that runs under the hood. Piss too many people off, and they may have a coup and throw you out of office. Having a strong military force is good, but that's also a source of bloody coups. And occasionally the people will call for elections--not having them will anger the people, but they may oust you from office if you haven't been treating them well.
Underlying all this is the ability to make Edicts, which let you do such things as fix the vote, take money off the top of construction, and so on. It may feel a little dirty the first time you have someone 'removed', but as the ruler of a small republic, sometimes it's the only thing you can do.
The game sports a complex system of Presidente creation, with a number of real-world characters represented as playable. They all have strengths and weaknesses, and it's necessary to adjust your tactics depending on how you set them up. Along with a handful of scenarios that come with the game, there's a strong random island configurator that lets you adjust the minerals, size, and difficulty of the game. It's eminently tweakable, and will lead to an enjoyable time for all.
Unfortunately, the 'endgame' is rather arbitrary, and you're basically scored on your performance depending on how the scenario or random world is set up. It's not particularly satisfying, but getting to the end of the game is fun enough to almost make up for it.