What five-year period do you think was the apex of the power of the following countries?
Geez, aren't your criteria a bit tight?
1945-1950
Reason: Relatively power vis-a-vis the rest of the world, the key role of the US in rebuilding (Western) Europe and Japan and propping up all the friendly regimes around the world. Never before had the US been so dominant and indispensable as in this period. Since then, its relative power has been gradually declining.
1910-1914
Reason: The British Empire was the dominant global power - politically, strategically, and economically. Some say that it was most powerful in 1919, after it helped won WW1, but since WW1 was a disaster for Britain in terms of human losses and the rise of economic dependence on the US, I tend to disagree.
Pf, I don't know. It could have been in the Middle Ages or in the Early Modern era. But I'd go with the Napoleonic period (before the war with with Russia), when France pretty much dominated the continent.
1555-1560 (5 years is way to short a period here)
Reason: Spain was reaching its highest territorial extent, and it was the dominant power in Europe.
a) 2010-?
b) 1910-1915 (dominant power in continental Europe, one of the largest and most dynamic economies in the world, a vast colonial empire)
c) 1937-1942 (almost complete control over Europe, in 1941 the most powerful country in the world).
1525-1530->1535
Reason: Battle of Mohács, near-victory at Vienna, seizure of Baghdad.
1950-1955
Reason: the heyday of global Communism dominated by the USSR.
Yet to come.