There are many good syslog handling tools, like Splunk:
http://forum.mikrotik.com/t/tool-using-splunk-to-analyse-mikrotik-logs-4-0-graphing-everything/153043/1
Problem is the logging mess that Mikrotik sends out. They told that they will look inn to this many years ago, but nothing has happen.
http://forum.mikrotik.com/t/logging-prefix-is-a-mess-sup-105353-sup-144261-waiting-for-mt-to-support-rfc-5424/111067/1
It may be fixed in v8 