1. go to q=admin/content/types and then click managed filed link of forum topic type
  2. create new field with name (for example) poll and save it
  3. when forum topic edited poll settings option showed so user can post the poll about forum topic
  4. create new Views in Fields add Fields: content:poll, in Filters: Node: Type = Forum topic, in Sort criteria: poll - votes asc (this mean that all poll will be sorted by number of total votes)
  5. In Fields formatter can be choose (for example question so the only question of poll is displayed)
  6. now you have the views that display questions of 10 most voted polls in forums