Did anybody actually see this in a theater?

Yes I saw part 2 and 3 in theaters and I think it was at the dollar theaters.

Sure did! I was pretty pumped for this, having read the novelization before it came out. I was 9- and just the right age for all of the 4-color future stuff, and action and humor. It was probably instantly my favorite movie at the time.

I recall my parents, especially my mom, strongly disliking the alternative 1985 sequences, which may have all been a reaction to Lorraine's plastic chest.

Over the next six months, I read the novelization for Part 3 and was really excited to see that one. However, it didn't quite click with me the way Part 2 did.

Over the next few years, I had a new favorite movie every year (Batman 1989 was a thing), and people seemed generally down on BTTF2 and I came to think less of it. Probably also related to how I felt let down by BTTF3.

But in adulthood, I have come back to really appreciate BTTF2. I think the first movie is possibly perfect, and while the second is definitely flawed, I think I actually prefer it.

It replaced the poignancy of "meeting your parents as teenagers" with MJF in a miniskirt and a wig. It replaced a simple plot complicated by 1 accidental time travel with perhaps the most original and bonkers tale of alternate realities and other selves in 1955. In addition to a nostalgic look back to the 50s, it includes an acerbic prediction/parody of the then near future. If the moral of the first one was "your parents were like you when they were young" and "be the best version of yourself your can be- it makes a difference!" then the moral of the second seems to be "don't mess with the space/time continuum" and "don't let your past self see you if you return to a previously visited timeline", which are arguably less relatable.

But I love it!

Oh, and that cliffhanger ending! What a finish! I've come around on 3 somewhat as well, though it remains my least favorite of the 3.

(To answer your question, I don't recall how full the cinema was exactly... But I think "normal". I probably saw it early, when it works have been pretty full, and then again later when audiences had waned a little)

Yes. My bro and I had free premiere tickets to "Working Girl". The film broke a half hour in. The mgmt said we could watch it but they'd have to start it over, or we could watch any of the other films in the theater (I don't think anyone stayed for Working Girl loL).
BttFPIII had a decent sized audience I guess. I think everybody was hyped up when the preview for III came up at the end but there were some disappointing 'awww's too because the film didn't wrap up.

I saw all three in the theaters. They were packed.

I did and I liked it, but was not happy about how Crispin Glover wasn't in it. I don't remember how many people were in the theater. It was so long ago, but I am sure that there were many less than when I saw the original. We sat in the front when I saw the original in the theater, because it was packed. I don't remember sitting too close during this one.

https://moviechat.org/tt0096874/Back-to-the-Future-Part-II/5ff99f7e26e5b56f7a376684/who-saw-this-in-the-cinema-back-in-89

I'd like to go.

I saw Parts I and III in the theater, but not Part II. Part II was released around Thanksgiving 1989 (if I remember correctly)...I was a junior in college at the time and just couldn't make it to the theater to see it, so I actually saw Part III without seeing Part II (Parts I and III were both released in the summer).

While watching Part III, the only thing I remember that came from Part II was The Hoverboard. I still could enjoy (and make sense of) watching Part III, even without seeing Part II.

I finally did see Part II on TV years later. I wish I had gotten to see it in the theater, because I bet it would have really played well on the big sceeen. I enjoyed Part II...but it's probably my least-favorite movie of the three.