Ответ:
1. The weather is better today than it was yesterday.
2. London is one of the biggest city in the world.
3. This sentence is more difficult than the first one.
4. This dictation is not so easy as the last one.
5. Which is the highest mountain in the world?
6. Your composition was the worst in the class.
7. I am not so tall as Jimmy.
8. This film is as interesting as the one we saw last week.