Doubt I could pick a single generation.
Third gen is special to me seeing as it was when I first got into videogames and I have many early, happy, memories of enjoying games on the NES.
Fourth gen was great from the whole Snes Vs Megadrive point of view. Still remember how stunned I felt when I first saw Super Mario World running on the Snes. And early on in the generation I used to love it when my cousins from Scotland (this was when I lived in England) would come down to stay in the holidays and bring their Megadrive with them. Not owning a Megadrive at the time made those rare occasions of playing Sonic, Streets of Rage, Toejam & Earl and Castle of Illusion all the more magical.
Fifth gen was home to The N64. Possibly my favourite games console of all time that played host to some of my favourite games ever.
Sixth gen was when I started to tire from gaming. I wasn't as interested in gaming as I had been. Well, I'd still play the N64 but current gen (at the time) wasn't as important to me as it had been. Despite owning a PS2, Xbox and GC. Still despite this feeling of appathy towards gaming I still had plenty of great experiences.
Seventh gen is important because it revived my love of gaming. Mainly thanks to the Xbox 360, online gaming and Halo 3. It brought me closer to some friends that I had drifted away from after leaving school. And got me feeling passionate about gaming again.