You guys are so sweet! Well, I don't know if I have a favorite game in the series, per se. I started with good ol' Blue Version, and then skipped gen 2 because I never had the money for those games. Then I picked up again with Sapphire, followed by LeafGreen, Platinum, both HeartGold and SoulSilver (HeartGold was stolen, SoulSilver is lost. Really sad stuff), Black, and now Y Version.
I'd say the new games are my favorite, just because of the fact that playing them reinstated that sense of awe I got when I first played Blue. There was so much detail, and the new 3-D models and moves all look so good that it's hard for me to go back and play the older ones!
And since everyone's oh-so-curious, my favorite types are Fairy, Grass, and Ice. I guess my list would be as follows:
Gen I - Articuno, Venomoth, Dragonair
Gen II - Sneasel, Meganium, Jumpluff
Gen III - Banette, Shedinja, Cradily
Gen IV - Glaceon, Roserade, Vespiquen
Gen V - Cofagrigus, Lilligant, Chandelure
Gen VI - Delphox, Dragalge, Florges
Out of all those, my top 3 would probably Glaceon, Banette, and Roserade. But anything past that, good luck getting me to order. :P