not sure what you're getting at. normally, what happens is, you dump the router logs into the syslog server. as such, you need to configure your router's syslog to point to the syslog server.
seems you're trying to get the syslog server to read logs from the router instead? syslog-ng don't do that.

ok, is the server behind a NAT? as in, can the router reach the server(ping)? did you allow the syslog port on the server-side firewall(internal/external)?

what was the problem?

to read the logs would depend on the syslog-ng config. i don't remember the default config, but syslog should put the logs into a directory somewhere in /var/log. you can filter the content by using hostname, IP, date blabla(in syslog-ng.conf). this is basically the "all manual way".

you can also dump the log into an sql database and use php-syslog-ng as the web front end. much easier to read.