If we talk about land size, Mongol Empire should have been more size.
If we talk about population England had more because they survived 700 years later!

I do not want to about culture any more, it is so subjective so it changes from man to man...
If we talk about political domination I would give my vote to:

15th 16th Century Ottomans dominated Europe, world is under debate,
17th 18 th Rise of Spain and Portugal as world powers and Rise of French Language in Europe.
19 th century for me the peak of England domination over the world, Europe is under debate.

If we talk about Cultural domination especially rise of English, I can say that from my univ. years that we discussed the topic for days, the Language itself started to dominate the world after successful colonialism of Britannia of Africa, India, America and Australia. World trade centers were on the hand of Englishmen so trade caused English's Inflation than of course literature etc. but even the golden era artistic works was not starred before 18th and 19 th century even Shakespeare became a world celebrity after 200 years after his death.