Not sure that you can something like this right "out of the box". It will require quite a research to do: I think you need to get the data from web analytics if it is enabled. You probably need to add a new field to page (CMS_Document), make it searchable, Have a task that daily collects data from Analytics_Statistics, Analytics_DayHits and updates your new field. If you don't have web analytics enabled you need to use Google Analytics API to collect the data and do the mapping. When you have this field in the index you can boost it in smart search results, i.e. document with higher number of views will appear higher in search results.