When I was in 1st-3rd Grade (2001-2004), my friends and I all played Generations I and II (the two were sort of clumped together for me. I started playing Pokemon in '98-'99 and G/S came out a year later. I was way too young to remember anything other than loving Pokemon more than loving my sister, who also played Pokemon) and slowly transitioned to III. And after 3rd grade, they all suddenly stopped and told me Pokemon was gay. :(
Pokemon Mansion. Holy SHIT. That place creeped the SHIT out of me. I went in and saw this decrepit place and was like @_@ WHERE IS MY EXIT. Seriously, that place, along with Lavender Town/Tower and Rock Tunnel are the worst places of all time T.T
Elite Four. I have a clear memory of a Pikachu using Thunder against one of Lance's Dragonites. And it didn't do shit. That thing was simply invincible to me.
Celadon Cave. My sister got there first in Yellow version and caught a Mewtwo who was later named "PowerfulPKMN." Infact, I still have that specific save on her Cartridge. My own Yellow version (indicated by the Rival's name, "FuckYou"), was left in my friend's car T.T
Nintendo has yet to replicate these sorts of moments where I'm totally lost in the Pokeworld and am desperate to get out. Disappointment.
My clearest memory of 9/11 was me right after my school ended and outside battling Erika with my Typhlosion in Gold version. Yeah, that's how close Pokemon was to me; more important than 9/11 ... >_<.