You can run a report on forms in Tools > Report Writer *if* the form is used at check out or on a product. To access this information, go to Tools > Report Writer. In the column's filter, there are options for both check out and product form fields. Forms that are used on custom pages do not have any reporting capabilities in the Report Writer.
However, if you need reporting capabilities for forms used on custom pages, you could try using a 3rd party tool - such as formsmarts.com
. You can paste that into the HTML tab of your text editor in Sites > [site name] > Pages > [page name]. Please see this blog post for more information: