Anyway, this debate has been played out so much already. People aren't likely to change anyone else's mind on it. And the "evidence" is typically anecdotal as you can't really directly measure popularity, only by using secondary indicators (like box office, merchandise sales, wait times for rides, etc) that have many factors that impact them. That said, I'm still gonna toss in my two cents...
Star Wars is quite a bit more popular. It's multi-generational, it's time tested, it's consistently generated craploads of revenue. Fandom ranges from various extremes but most people are at least casual fans of the series and have some cultural awareness. Most anyone can tell you something about the Force or lightsabers or Jedi compared to stuff from Potter (it's tough to say the equivalent -- maybe like a Patronas spell or Dementors or Aurors).
I expect Harry Potter to remain popular, but I think long term it will be more like Hobbit/LOTR in terms of it's cultural penetration. Something the general public is aware us, many people have seen the films and could name some stuff, a lot of folks will continue to read the books but not like it has been in the past. I think its hardcore fanbase is much smaller than SW and is probably not growing like that of Star Wars which keeps adding in new generations. We'll see of course what happens.
That all said, I think WWOHP was a bigger phenomena than SW:GE will be, at least in terms of their openings for a variety of factors:
1. There was a huge pent up demand for Harry Potter "stuff" -- experiences, merchandise, etc that was completely unmet at the time of the land opening. That's why there was the massive line to see the park. Compare to SW where you already have theme park rides and experiences, where you have had continuous conventions for ages, where you could get pretty much every piece of merchandise you could want over the years. It was pretty easy to come up with merch for Potter since nothing really existed and going to Uni was the main way to buy most anything Potter branded. Meanwhile, I could go to Target today and find Star wars stuff in so many different departments -- toys, home goods, electronics, sporting goods, whatever.
2. People really want to "visit" the specific locations of HP. It works out so well for theme park lands. As many have mentioned, it doesn't work for SW since the locations themselves aren't the draw and they are varied and not iconic. The enthusiasm for visiting Batuu is not the same for going to walking the halls of Hogwarts. (I do think creating a Millennium Falcon ride where you are in the corridors of that ship is the closest equivalent for SW and think it is great they are going that route).
3. Potter works better as an immersive experience due to it being a place on Earth with just some different rules, but where the story often involves mundane things that translate easily (riding a train to school, eating/drinking, going to class or work) as opposed to a war torn alien worlds.
4. Having two different lands opening up close together will spread out the SW crowds more than HP where there was only one location for many years.
It's going to be an interesting thing to watch to be sure.
