Chrono Break.
For real though, I never endured a harder wait than Pokémon Gold and Silver.
Hear me out. I was 11 back in 1999 and everyone in school, i mean EVERYONE, was playing Pokémon Red and Blue. Proper craze. My parents got the Internet by spring 1999 and let me tell you I was the coolest kid because I was one of the few. The rich kid next door had the PS1 and the N64 but I had the Internet!! We started looking for Pokémon stuff online (that darn truck) and we stumbled upon the infamous Pikablue, Ho-oh... and a couple of others. That was our breakthrough. We printed the webpage and the next day, at school, we told our friends about our findings. There were not 151 Pokémon but 156! Comes december 1999, we find out about... a new Pokémon game. Already released in Japan! The best bit? The rom was downloadable!
For a few days, we were the kings of the hill, telling people about this new Pokémon game, Gold and Silver, playing it... except we're not fluent in english, and it's not even fully translated. And then we realize : the game is set to be released in... 2001. This is december 1999! How are we supposed to WAIT?
The day I grabbed my copy of Pokémon Silver was one of the best in my whole childhood, but man, being able to play the game before it got officially released in Europe added a special bond between Pokémon GS and me. I felt like this game was made just for me, and the day it got available to everyone, it really, really felt like introducing a very good friend to all your other friends. What a crazy wait.