(When I say Star Wars, I am talking about the original three movies.I meant to write this up this summer, when I sat down and read all 7 Harry Potter books back to back. It obviously didn't happen, so I'm throwing it up now. And when I say Star Wars, I am talking about the original three movies.)
I was struck when reading the books at how many similarities there are between the Star Wars films and Harry Potter. This post got very long but I'm still fascinated by the notion. There are spoilers in here, but if you haven't read all of Harry Potter or seen Star Wars by now, you aren't going to anyway.
the very idea that these projects are similar is easy to see once you stop and consider it. But, because people have become very invested in them, it's easy for these fans to throw the notion of them being related out of the window and pick at the details to refute the argument. That's a shame, because it's the bigger picture that actually makes this interesting than disputing little details. As opposed to, say, whether Han and Luke were best friends or Hermoine and Harry were siblings. (Though I'll mention this again at the end. And I find I still come down on the side of "they are more alike, even here than not.")
A quick Google search turns up that I'm not the only person to notice this:

from: Say No to Crack » Blog Archive » Harry Potter and Star Wars
This picture is funny, but it's clearly dated — in this version, the becomes about winning the cup, not defeating You-Know-Who. So we dig a little deeper.
Although too large to fit on the page here, there is a chart outlining the Hero's Journey by Campbell as it relates to sci-fi movies. Of course, Star Wars is listed first and it has "x" for all the following steps, save "battle with brother":
- hero called to adventure
- hero refuses call
- hero finally answers call
- hero meets "guide" figure
- hero finds companions
- hero crosses into adventure
- meets threshold guardians
- enters belly of whale
- road of trials
- battle with "brother"
- meeting with goddess
- night journey/abduction
- dragon-battle
- death of guide/hero injured
- apotheosis
- ultimate boon/elixir
- refusal of return to danger
- rescue from outside source
- crossing return threshold
- master of two worlds
Read that list a second time. If you are familiar with the Potter, this should almost strike you as an outline for the storyline. Of course, if you aren't familiar, this whole post is lost on you.
Let's step through these quickly and see which ones apply to Potter. (I don't want to argue about whether the chart has Star Wars right or not. For instance, meeting with goddess? That can only be Leia and I would argue that she isn't a goddess at all.)
Potter clearly called to adventure. He doesn't refuse the call however, he welcomes it. He does meet a guide figure and companions. And he certainly crosses into adventure. That takes care of the first book. This middle bit is tricky because we have 4 or 5 books for these items to happen. And I would argue that you can find evidence of all of them happening ("dragon-battle" anyone?) I do want to say that "meeting threshold guardians", "road of trials" and "battle with brother" are all very valid here: Harry defeats Voldemort's horcruxes, which are certainly Threshold Guardians. The entire middle part of the series is a road of trials. And Draco isnt a far cry for a brother figure.
And then we hit the last two books. "Night journey"? I'll argue the first half of book 7 might fit. "Death of guide"? End of book 6, bingo. "Apotheosis"? Well, that's there from the start of the series — Harry has been deified before he has even been called to adventure. "Ultimate boon"? How about 3 of them in Book 7? "Refusal of return to danger"? Maybe not as much, though standing around in tents and arguing might qualify. "Rescue from outside source?" "Returning to the threshold?" "Master of two worlds?" Oh my yes. That's Book 7 right there for you.
Looking a little deeper into Campbell's Monomyth brings up some other points. If you are interested, check out the Wikipedia page on Monomyth — it says this "The monomyth structure can be found in many popular books and films, such as the Star Wars and The Matrix movie series, and the Harry Potter series of novels." I'm not going to regurgitate it all here.
Finally, there is a thread on the official Star Wars boards about the similarities between the two. This is more interesting, as they are more direct than Campbell's points.
The 10 they list are:
1. Orphaned by a Dark Lord ("Luke Skywalker and Harry Potter both grew up wistfully curious about the parents they never knew.")
2. Relative Obscurity ("As children, both Harry Potter and Luke Skywalker lived under the hidden protection of an aunt and uncle, longing for a better life.")
3. "V" for Villian ("The main villains of the Star Wars and Harry Potter universes often change their names, personalities and even appearances upon turning to the dark side.")
4. Who wants to live forever? ("The Emperor and Voldemort were both obsessed with immortality, eventually returning from death to continue their quest for eternal life and unlimited power.")
5. Romancing the Stars ("Luke Skywalker and Harry Potter both had a male friend and female friend who initially annoyed each other and bickered often, but ultimately fell in love and got married after hiding their true feelings for years.")
6. Dead Mentors, Dementors and Frozen Friends ("Being associated with either Luke Skywalker or Harry Potter can be hazardous — both had teachers who were murdered, both had friends who were frozen by the enemy and both had family members who were caught in the crossfire")
7. Like Father, Like Son ("Harry Potter and Luke Skywalker, like their fathers before them, were both gifted pilots who displayed special talents long before they knew of their hidden abilities.")
8. Love Hurts ("Both Luke Skywalker and Harry Potter suffered a string of physical injuries that left them permanently scarred.")
9. Size Matters Not ("Star Wars and Harry Potter both featured a wide variety of height-challenged characters and species — and Warwick Davis portrayed many of them.")
10. Your Father Wanted You to Have This ("Harry Potter and Luke Skywalker both received mystical heirlooms left behind by their late fathers, presented to them by elderly mentors.")
Sure, 9 is (very) weak. But most are dead-on. I especially noticed the whole aunt/uncle thing, along with the Obi Wan/Dumbledore connection when I was reading the books, along with the basic duality and the whole "You killed my father!".
I'm not suggesting Rowling ripped Lucas off. But I do think both of these series touched nerves for some of the same reasons. And those reasons come down to structure.
It actually goes farther than that. If you read Campbell's great book on hero archetypes, you'll see similar threads running throughout history. It's not just Rowling borrowing off Lucas; it's both of them borrowing off of archetypes which Jung would assign to the collective unconscious–part of why these heroes have such broad and lasting appeal. Campbell even relates it to Christ and earlier Greek mythology.
Yeah, that's why I didn't want to get too into Campbell. Its why I found the list from starwars.com to be more fun — those aren't Campbell's work and the overlaps are quite noticeable.
Ah well, now you just think I'm unedumacated.
no, no. I've _always_ thought that.
=)
I suppose what I'm saying is, it doesn't matter where the list comes from, either directly from Campbell or from a Star Wars board. The foundations are the same and predate us all.