Linked to below are the latest Whole Product Dynamic Test results published by AV-Comparatives. This is a measure of how well AV programs work. The test takes into account all aspects that any particular product uses to give protection. Only paid products are tested but I expect the free versions of programs use the same detection engines as their paid versions. No figures for Microsoft Security Essentials unfortunately:

http://av-comparatives.org/en/comparativesreviews/dynamic-tests

When on the page, click the 'Monthly Results' link.