I'll agree with Apache. I was a senior at A&M that year, and Batman was literally everywhere. Growing up, I had loved the first two Superman movies. Those were the only big-time movies made of a comic book character in modern times, at the time. I remember reading about a Batman movie midway through the '80s, but was always frustrated when news would say the project had been grounded. But then some time in '88 buzz about Batman coming to the big screen returned. Tim Burton had just done Beetlejuice, and was announced as the director. At some point it was revealed that Michael freaking Keaton of Mr. Mom had been cast as the caped crusader.
That casting really didn't go over well. I remember a song playing on the radio as the spring of 89 lumbered toward the summer and the June release, with lyrics whining about wanting Adam West in the role again. But by that time I had jumped fully on board with the casting, as I'd seen something on TV in January '89 that featured some footage from the upcoming movie. Let's just say that the footage blew me away.
At the time I worked for the Schumlan 6 movie theater that was located on E29th in Bryan. I remember being aggravated that the owner had opted against booking Batman because he didn't think it was going to do well (he thought Ghostbusters 2 would bring in huge money, and that, along with Indiana Jones and the Last Crusade, was his big booking that summer). The theater at Post Oak Mall booked Batman. That was a 3-screen theater, and the movie played on all three screens opening weekend. (June 23 was the opening, and Schulman started Roadhouse at one of his theaters - good movie that no one in town bothered with for a couple of weeks).
Batman '89 was a huge event. As others have stated, it was pre-internet, but the hype was equivalent to what we've seen with the Infinity War/Endgame type of Marvel movies. For movies released last century, I'd say Return of the Jedi, Batman, and The Phantom Menace are the only ones that could closely approximate the hype we see these days.
I really enjoyed Batman '89 at the time, but it has not withstood the test of time. The sequels all sucked ass. Well, Batman Returns was decent up until the flock of penguins waddled out with rockets on their backs. The two Joel Schumacher movies were God-awful pieces of dog crap, but he did lead the series toward more of a TV-series look and feel; I'm honestly shocked he didn't pull out the Biff! and Crash! placards during the fight scenes. I rank Batman & Robin as among the worst three movies I've ever seen, and because of that, when Batman Begins came out in 2005, I very nearly skipped it. Someone finally talked me into going on what turned out to be its last night in the theater here in Katy, and damn, that was a Batman movie worthy of the name again. The Chris Nolan series put the final nail in Batman '89's coffin.
Batman '89 was a singular movie experience at the time, but it didn't last. There was no hype as far as I was aware in 2008 for Iron Man, a movie I did not even see until it released to video. But with each subsequent release, I was getting more and more invested, and when we saw Thanos in the end credits of the original Avengers movie, they had successfully hooked me. I won't say there was any real hype for most of those MCU movies, other than perhaps Captain America Civil War, but always in the background there was the promise of Thanos, so that by the time Infinity War released, the hype was through the roof. The MCU hype was really a hype of a promised future that everyone knew was coming, and when it finally came, the hype exploded and they knocked it out of the park.