My very first Pokemon game (and also my very first game ever) was Pokemon Pearl in 2007.
I started on Gen IV and then went backwards from there. My next game was Fire Red, then I got Leaf Green, then I got Emerald, then I got Gold and that was it for main series games until last year when I got White 2. Not sure whether I'll get Omega Ruby or Alpha Sapphire yet, but I'll get one of those.
Anyway, Pokemon Pearl was my first game ever, and I still manage to play it and find it fun nearly a decade later. :D