Can I display some products on top of the list in spite of actual bestsellers data in magento?

To achieve this you need to create a custom attribute for bestsellers and enable it for using in Sorting options: catalog > attributes > manage attributes

Product with values set in the custom attributes will be shown on the top of the list, while the remaining products will be sorted based on actual data. Please see more details on how to create custom attributes for bestsellers and most viewed options in our User Guide on Product Sorting.