George Lucas, on his own, made a wonderful and iconic trilogy, and he certainly will be remembered as a visionary with a massively successful story.

However, let's look at his career. He got his break with a movie that is really not good, American Graffiti. It was an instant hit at the time due to Lucas' ability to target a particular generation (those in high school in the late 1950s/early 1960s) at a time in their lives when they felt a nostalgia for their high school years. I have yet to find a lot of people in younger generations who have any strongly positive feelings about the movie.

Then let's look at the Star Wars trilogy. Lucas only directed the first movie of the trilogy (in fact, according to Wikipedia, Lucas has only directed six movies in his entire life). And while he wrote the screenplays for all three, let's not forget how bad some of the lines really are. He directed and wrote all three of the second trilogy, but I think we can agree that, although commercially a success, the writing was even worse and the movies had mixed reviews.

He also wrote the screenplays for all the Indiana Jones movies (including the fourth one that many wished never existed).

Other than that, he hasn't really done much except act as a producer (read: paid for the movies in question).

He certainly isn't "the most influential filmmaker of all time". His studio may have had an influence, but again, that's not Lucas, that's a studio he set up.

If I had to pick someone, I'd pick Martin Scorsese. His movies are at once blockbusters, entertaining, and also significant in a deeper sense.

Look at his first big movie: Mean Streets, for which he was the director, writer and producer. While not as fully developed as later pictures, it certainly beats American Graffiti in all categories, and it launched De Niro's career. Then let's look further

As writer, director and producer:

Goodfellas

As writer and director:

Raging Bull
The Last Temptation of Christ (co-writer)
Casino
The Age of Innocence

As director:

Taxi Driver
The Color of Money
Cape Fear (remake)
Gangs of New York
The Departed

He has directed 22 films (to Lucas' six) and almost every single one is nominated for awards as well as making a decent showing at the box office.

Other options that easily beat Lucas in terms of significance include Coppola (who directed about 27 films by my count, produced countless more, including Lucas' dubious American Graffiti, is known for such classics as The Godfather trilogy, Apocalypse Now, and was the screenwriter for Patton), Woody Allen (over 40 movies and he keeps going, so many nominations for awards I can't even begin to name them all), or Hell, how about John Ford, who directed over 140 movies, including greats like Stagecoach and The Grapes of Wrath? What about Spielberg, who directed all the Indiana Jones movies but did tons of other iconic movies, like Schindler's List, Jaws, E.T., Close Encounters of the Third Kind, who wrote Poltergeist?

Lucas had one big hit, and yes, it was huge, particularly when we look at the residuals (the toys, the books, the cartoons, the costumes, the comic books, the fandom, the geekdom), and yes, his special effects studio is now ubiquitous, but as a filmmaker? No way. Not even close.