Zelda: Ocarina of Time for me.
Ever since that tech demo of a super blocky Link fighting a knight was shown in 1995, I spent days looking at magazine screenshots and any info I could get about the game. It got really bad as the years went on when more screenshots started coming out.
During summer break from school, I would literally wake up at 5am, go outside, sit on the porch and catch the sunset while looking at OoT (and Mario 64) screenshots from multiple magazines.
Of course, the name would never live up to the game I had created in my head, specially since most of those places from the early years shown on screenshots were never in the final game. Something like that happened with Twilight Princess too. I don't remember obsessing that much over it, but the game was disappointing too due to how hyped I was for it (and how long I waited for it).
And now we come to BotW. I've been waiting for 5 years now, and my levels of hype are matching or surpassing my OoT hype. Thankfully all impressions from people that have played the game are positive and the game has enough advancements and new stuff (for a Zelda game) that I think this one will not be affected by my hype levels.