To get your site delisted by Google, you will need first ensure that your site is clear of any infection, the safest way to do this is to delete all the files first and then re-upload your copy of the website.

Refer to the following pages supplied by Google to help get your website removed:

First Step:

Add Website to Google Webmaster Account

Webmaster Tools can be accessed via the URL: https://www.google.com/webmasters/tools/

Next Step:

About malware and hacked sites

Last Step:

Request a malware review