"The ground does not shake as the Big Sight approaches. That is only the sound of my heartbeat."
Comiket was, in fact, terrifying. I know of nothing even remotely comparable. I did not actually see the crowds and immediately flee in terror, but I came pretty close. Even at the beginning, as I watched the Tokyo Big Sight rise over the bay, I felt the first stirrings of blind primordial panic.
The problem is that, for all my serious devotion to fandom, I don't actually like very many things. In aggregate, things that I don't like (such as Shonen Jump series) are virtually all of Comiket. But Comiket is special. I had to go, no matter what, just to see it and understand where we all came from.
And so I did, for two days.
Several times I was picked up bodily and carried with the crowd for a span of several paces. Once this happened while a guy was demoing a desktop mascot, and I shrugged, gesturing at the crowd as I was carried past. He smiled, shrugged back, and we bowed, me as best I could. At times the crowd was so thick that I couldn't even see the booths, much less the merchandise. Attempting to cut through would have been folly.
And yet, like any description that emphasizes some particular characteristic of a thing, it would be oversimplifying to say that there are large crowds and long lines at Comiket. There are, but there are also aisles that have only a few dozen people, where the circle participants chat, or draw, or type into their mobile phones. Some parts are crowded, but there are always little islands of peace, even at something like Comiket. I think that focusing on the crowds misses the point -- Comiket is large enough to have diversity. It's an entire world, and I'm looking forward to going back.