select project_id, service_id, count(*) as count
from tbl group by project_id, service_id
order by count(*) desc
Bare tilføj service_id
til din group by
og select
liste. Det burde gøre det.
REDIGER -
Ifølge kommentar fra @Rajah
det ser ud til, at du skal bruge
order by project_id asc, service_id asc