Transform the sentences as per directions given in brackets:
Very few poets of England are as great as Milton. (Superlative)

The given sentence uses the positive degree of the adjective 'Great'.
The superlative degree of the given adjective is 'Greatest.

To convert a positive degree into superlative degree, we use the structure:
Clause 2 + Superlative degree + Clause 1.
Example:
No other girl is as brave as Sheela. (Positive)
Sheela is the bravest girl in class.(Superlative)
Here, the sentence uses the phrase 'very few', which suggests that Milton is 'part of a group that is the best'.
So, the sentence becomes: Milton is one of the greatest poets of England.