Going back in time... after the period of time which is commonly referred to as 'Imperialism', the series tackles the European takeover of the American continent (or a random world substituting for the 'real' one).
The reliable and tested foundations of the predecessor are still there in pretty much the same way. Economics are based on basic production chains (harvest raw materials, transport them to your capital, produce something from them, with the work being done with more or less trained or specialized workers), just that the materials and products differ slightly.
One definite improvement is that the 'new world', i.e. the minor countries which are waiting to be conquered have some 'exotic' goods, like for example tobacco or furs, which aren't readily available in the 'old world'. That's one complaint less: an actual difference between core and non-core provinces. Since those goods from the colonies are essential to get more effective workers, expansion in that direction is practically forced on the players. Not just to get them for oneself, but maybe also to cut off the competitors from that supply...
The military part is still split into strategic planning on the world map and tactical battles. The difference between 'old' and 'new' countries strikes here as well: The 'American' provices are defended by special units not available to Europeans. These are quite weak - which may be realistic, but it causes one strange effect: It's actually the most effective way to conquer the provinces overseas (since their defenders can be taken out with a tiny army), but make colonies of the minor countries of the old world (which still exist, too, but they, of course, have European military, too). Twisted.
A very welcome change is that the council election for the game winner has been scrapped. Instead, control of most of the 'old world' is required to win. So no losing the game in spite of almost total dominance anymore.
Gameplay-wise, both major concerns of the predecessor have been adressed, however there's still room for improvement. One is the game / map flexibility. The randomized worlds are all very much alike. What about countries spanning more than one island, for example? Not possible. What about continents which are really far away from the rest of the 'world'? Never happens. What about different target continents for expansion, which again differ from each other regarding the goods you can get from there? Not included.
Another gameplay aspect which would be appreciated is population. Once you've conquered a province, it's just yours, no matter who lives there and how these people like your government. In the same vein, actual colonization (i.e. sending settlers) isn't included.
So Imperialism 2 isn't a major step forward, because the improvements are fairly minor. That combined with the purely subjective complaint of mine (that the era of industrialization (covered in the predecessor) is just more interesting than the 'age of exploration') results in a game which is pretty much on the same level quality wise: excellent, but not perfect.