To list all loaded services on your system (whether active; running, exited or failed, use the list-units subcommand and --type switch with a value of service.
# systemctl list-units --type=service
OR
# systemctl --type=service
And to list all loaded but active services, both running and those that have exited, you can add the --state option with a value of active, as follows.
# systemctl list-units --type=service --state=active
OR
# systemctl --type=service --state=active
But to get a quick glance of all running services (i.e all loaded and actively running services), run the following command.
# systemctl list-units --type=service --state=running
OR
# systemctl --type=service --state=running