What it was like
The line forms before dawn and nobody standing in it is unhappy about that. Somebody passes back a folding chair. Somebody explains a costume they spent months building to a stranger who genuinely wants to know. This is the part outsiders never understand — the waiting is not the tax you pay for the convention. It is a large part of the convention.
Inside, the San Diego Convention Center holds every fandom at once and refuses to rank them: comics, anime, science fiction, fantasy, gaming, all of it running at the same time across panels, sneak peeks, and floors of merchandise you cannot get anywhere else. The biggest names in entertainment come here to say things out loud for the first time, and one aisle over an independent creator is selling you a book they drew themselves. Both happen in the same building. That is the actual miracle.
Cosplay in every direction, collectibles, and a city that hands itself over for the weekend.
Go with the person who got you into all of it.