Star Wars but with a qualification - I'm referring only to the original 1977 movie, and comparing it only to the original Star Trek TV series. Star Wars had an incredible impact on my (then) young and impressionable mind. I grew up watching Star Trek on TV, and it's still fun to revisit the original series, but I hold it in the same regard as other TV series of that era. Star Wars transformed science fiction and the entire movie industry. Its impact is unparalleled.
If we're talking about them both as complete intellectual properties including all movies and TV series combined (Star Wars has had multiple animated TV series) I'd give the advantage to Star Trek. In terms of the sheer quantity of TV episodes, there are more good stories and characters there, and far fewer stinkers (although Star Trek certainly has its fair share).