You are judging the Greeks to be the most influential because of they originated this one word "philosophy"?By the fact that Romans or Roman modern western civilization have not be able to find another non-Hellenic term for this so important sense, over the last millenniums?
I voted the Romans partly because the philosophy that arose under them, and established by them, Christianity, dominated Western civilisation for over 1000 years. Which Greek philosophy held any real influence in the past 1000 years?
The Greek writings and artefacts we have available are mostly of those things that the Romans selected and copied.
The buildings that the Romans made throughout most of Europe have had a huge influence on Western civilisation.