Probobly because AC GCN has actual holidays, and it's got a warmer, more homy feeling. And now, with Wi-Fi in ACWW, everything a competition to people...they all wanna compare items, towns, ect.
ACDS felt like a cheap knockoff compared to the original, It's an alright game, but the GCN version just had so much more in it... I figured it'd be better somehow... more fish, more bugs... wifi... but then it died about a month later when some people cracked it with SD readers, its since become one of my lesser played DS games, but then again, i don't really play DS at all anymore.
ACWW: I think it's better because there's more to it such as the Wifi and Slingshot, instead of waiting for a balloon to come in a tree. It also has a better feature of every acre you move, you can move freely, instead of waiting for the screen to go into the next acre.
AC: I sort of liked how you could use the cheats to get furniture, off of Tom Nook, but then it seemed pointless and it kind of recked the game if there is no point in collecting furniture.
This is just 1 of those games that goes on and on and somehow looses interest. I'd say that ACWW is better out of the two.