Kudos to Will for not mentioning a year from his childhood.
I honestly have to agree. 2000-02 was magical as far as I'm concerned. Marvel and Vertigo were doing really exciting stuff, every single week. The movie theaters were full of LOTR movies and the early X-Men/Spidey stuff (which I still rank near the top of the comics films) and more. Harry Potter and Game of Thrones were in peak form and not yet ruined by hype and adaptations and mediocre entries. The best generation of video games just started up. If music counts, then it was the peak years for giants such as OutKast, Missy Elliott, Jay-Z, Radiohead, and a lot more. I really miss those days.
For the sake of this thread I'll go with 2001, as that is when Fellowship of the Ring and the Gamecube came out (within a month of each other!). Going to Fellowship with my friends was probably my pinnacle geek moment—nothing before or since has matched it for pure glee. I was 26.
EDIT: For formative years, I'd have to go with 1984: Ghostbusters, Gremlins, Temple of Doom, Terminator, Search for Spock, Neverending Story, Dune. For music I think it was objectively the best year for radio pop. Arcades were hopping. And comics, well we all know what Marvel was up to with Claremont, Byrne, Miller, Simonson (although I was mostly reading GI Joe, Conan, and Elfquest at this point).