obviously a very debatable sentence, but i'm not sure anyone since griffith has propelled film forward the way he did. it's become a cliché to say it in every obituary but he really did change the landscape of cinema and basically created the filmic 'language' that took hold over the past half century, even as he himself rejected a lot of his own 'lessons' and constantly sought to push further into new territory. it's wild to consider the diverse range of directors who were directly and strongly influenced by him: tarantino, wong kar-wai, kiarostami, fassbinder, scorsese, von trier to name a few. tarantino's probably the best analogue for his initial run though; he was essentially the QT of the '60s in terms of spirit and impact, only when he was doing it it was a much bigger leap, and had far more weight and purpose intellectually and politically speaking.
and obviously, he was part of the single most important movement in the history of film criticism as well, so his influence goes beyond his filmmaking. he played a very big part in rescuing the reputations of the likes of hitchcock and hawks, who subsequently influenced probably 75+% of beloved films nowadays (no lynch without hitch, no carpenter without hawks, etc). so i reckon in terms of overall impact and influence there are very very few above him.