*looks at her game collection* Er, I have:
Red, Blue, Yellow
Gold, Silver, Crystal
LeafGreen
Emerald (+ bid on Sapphire on eBay atm)
Diamond, Pearl, Platinum
HeartGold, SoulSilver
And I'm planning on buying Black and White. =] All I can say is, thank Io for eBay and CeX; that's where most of my games come from. I only bought Gold a year ago and it was new in the box, sealed! So that was fun. But yeah, I like having all of the versions of each Generation because then I have all of the Pokémon aside Events.
Of course, it is just a marketing ploy on Nintendo's side (and a damn clever one) but at the end of the day they don't make anybody buy anything, so I'm cool with it.