OK, now I have played more than 200 years of a Grand Campaign as France (Normal/Normal, my first GC, for learning purposes), so I may finally claim some insight in this matter.
The 'strategy' text for France in the start screen says something along the lines of 'France has a very good chance of becoming a superpower, which can only be stopped by an alliance of nations'. I found this to be true; in the early 1700s, my France is an absolute behemoth of unparalleled military and economic power. In addition to the starting provinces, France controls most of what used to be Spanish Netherlands, Italy all the way to Rome, all of what used to be Venice, Switzerland, the Southwesternmost provinces of Austria (Tyrolia + the one producing gold, the name of which escapes me now). Furthermore, a good chunk of the small states of the HRE are either vassals or annexed provinces, and I also have a rich (although not enormously large) colonial empire.
I'm not trying to pass for a strategic genius, this is all because France is easy. *Really* easy. At least if you don't run into an united allied front in Europe – and at least this time around, I didn't. Spain was powerful early on, but then the southernmost provinces declared independence, and it was all downhill for the Spaniards from there on; the Iberian peninsula wasn't big enough for three (or four – France has a foothold there as well), and Spain, spread thin because of rapid colonial growth, was in deep trouble with Portugal and Granada (and France). Aside from grabbing a few provinces from Spain, Portugal didn't seem to have much ambitions, military or otherwise, in Europe, but was able to put together a flourishing colonial empire; they seemed to view Spain as their main adversary, and once they were reduced to a shadow of their former glory, they did not seem interested in the rest of Europe.
England was weak in the beginning, and I drove them out of continental Europe very early (and also annexed their ally Navarra in the same war, which was nice). After that, they were kept busy by the Scots in the domestic front and the creation of a large colonial empire outside the British isles. Most of the time they did have an alliance with Portugal – an ideal ally for a country which didn't seem to care what happened in Central Europe.
Austria was initially busy with annexing Bohemia, then Hungary (not diplomatically but in a war – they ended up on opposing sides in a war between two alliances), and finally a good chunk of Poland and a few provinces from the Ottoman Empire. It looked like Austria viewed the last two as their most significant threats, and they managed to strike severe blows against both, thanks partly to their alliance with Russia (France was also involved in the late 1500s, but in name only). In the late 1600s, Austria and Russia had jointly conquered most of Polish territory, and were then thrown into a war against each other – a war which failed to produce significant results one way or the other, but was nonetheless a significant drain on both countries.
The Ottoman Empire got beaten in the European front, even though they still managed to hold on to most of the Balkans. They did enjoy some success in fighting the smaller islamic countries, but even if they had wanted to, they, like Russia, were geographically too far from France to stop the French expansion in Central Europe
Sweden became the most prominent power in the Baltic Sea, but they couldn't expand to Central Europe. Saxony united most of the small states in Northern Germany, and was in fact powerful enough to stop the advances of Sweden through Jutland and other formerly Danish territories (Danmark itself was reduced to a couple of island provinces south of Skåne, thanks to Saxony). Russia did the identical trick in Karelia.
The reason I went through the above was this: I don't think any of the other powers acted in an unrealistic or idiotic manner. They were all either fighting their 'natural' enemies or concentrating on gaining territory in the new world. What they *did* do was look the other way while France took its first steps towars a superpower status, and then keep looking the other way while we whipped or bribed a large part of Europe into submission. While I think that I shouldn't have faced hostile alliances because I just completed my first annexation or simply because I'm the human-controlled country, I should have faced a strong, united front *at some point*, because I was clearly running away from the pack in terms of power. Not everyone hates the supreme number one nation, but to keep things interesting, it should always have a strong opposite pole, either a close number two or a number of smaller countries acting as one.
