Out of all of the people that have ever lived, did/do more of them speak modern English than any other language? There are 2 billion English speakers alive today, but in my brief search I wasn't able to find data on the number of speakers throughout history.
This is an interesting question, though it really is a question of history or statistics, rather than linguistics.
The "most spoken language in history" is certainly a modern language, just because the world population increased exponentially in the past few centuries.
Most human languages last for a few hundred to a thousand or so years before it evolves into something unrecognizable. But any historical language, even if it was around for an unusually long time, probably didn't have as many speakers as the largest languages today simply due to population math (remember that the population of the Roman Empire was well under 100 million at its peak!).
Basically the problem amounts to an "area under the curve" problem for the population of speakers of a language plotted over time.
I think the answer is probably Chinese. Even today, Chinese may have more speakers than English, depending on which estimate you're looking at (and it certainly has more native speakers).
However, the population of China has been at least several hundred million for the past 300 years or so. The population of English speakers was low until recently: probably just over 20 million in 1800, and around 100-200 million in 1900. (using rough estimates of the population of the US, UK, and its colonies)
(Note this still applies if we restrict "Chinese" to Mandarin and everything intelligible with it)
Do you mean 'most' as an absolute number or as a percentage of world population? The other answers seem to interpret it as an absolute number so I will look at the percentage.
The proportion of the world population that lives in China has varied from around 20% to around 40% from 400 BC until now (source wikipedia). English on the other hand only existed from around 500 AD and only become a prominent language in the 20th century.
So throughout most of the last 2500 years Chinese was the most spoken language in the world. Even today Chinese has significantly more native speakers than English (or any other language). Only very recently historically has the number of people who speak English surpassed the number of Chinese speakers.