Which is the most effective thesis statement?
fdr was the greatest president because he had a huge impact on history.
fdr was the greatest president because he served four terms.
fdr was the greatest president because he established unprecedented measures that end the great depression.
fdr was the greatest president because he brought about many positive changes.

I would say "FDR was the greatest president because he established unprecedented measures that helped end the Great Depression" because its the only one that demonstrates even a basic knowledge of what he did in office. To be honest though, all four theses are pretty weak. I don't know what course you're taking, but in an APUSH class, most if not all of these would get a zero.

The goods the europeans wanted the most were gold, jewels, silk, perfumes, and especially spices.