Eh, I never really played the games past the 2nd generation. I had a ton of fun with Red and Gold (and a bit with Yellow, but goddamn you Sabrina and your level 50 Alakazam). They had a charming simplicity to them, and given that I'm a compulsive min/maxer, this was a good thing - less minute little statistics to worry about screwing up, just catch 'em and go.
I never really got into the 3rd generation games, though I did get to the end of the Elite 4 in FR. I did, however have a lot of fun goofing around in NetBattle in this generation. I especially loved trolling the rampant DD Gyrados/Salamence with my Counter/Whirlwind Hariyama. Those were the days...
Gyrados used Dragon Dance! Gyardos' ATT and SPD rose!
Hariyama used Whirlwind! Gyrados is blown away!
And then when he comes back out again...
Gyrados used Hidden Power! It's super effective!
Hariyama used Counter! Gyrados fainted!
The enemy player disconnected!
Yeah, those were the days.