There is no functionality to compare revision history of pages, only content items revision history is comparable, here
is the documentation on this. The lack of comparison for pages is not something that have changes, there is no comparison also in older version like Sitefinity 6.x .
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items