Report: Activity log for all known leads

The only way to get web activity out of Marketo for each lead is to export their Activity Log, but that is not practical beyond a handful of leads.  There might be some other solutions that don't include having every web page visit in a report, but I'd need to understand what the data will help you do.

We are determining a few things including what pages do the leads look at before they fill out the form, all original referrers, paths that each lead takes before they fill out the form.  I started exporting web activity for each lead and that was turning into a nightmare so any help on how to expidite this process would be greatly appreciated!!

You should be able to at determine this in Google Analytics. Set up your form submission confirmation landing pages as Goals in the Conversions | Goals | Goal URLs.  Then in the Reverse Goal Path, you can see the pages that were visited prior to reaching the confirmation landing page.  Below is a screen shot of that page.

We would like to be able to associate the web activity with specific leads so we can combine it with pipeline value when the lead converts.  Is it possible to see who filled out the form through GA?

GA doesn't provide lead specific data.  You can get program analytics via Revenue Explorer tied to lead convers and you should be able to infer correlations between paths that leads took to forms that resulted in pipeline or wins.