I in fact did complete the National Pokedex in Platinum, complete with event legendaries, just a few days before the european BW release. I also completed the BW1 and BW2 local pokedexes, but with the help of WiFi 150 pokemon are nothing. I was honestly surprised when I realized I was done, since I never completed RBY's dex - but that was due to local restrictions. I also completed Crystal's pokedex, except for Celebi. Took quite a while tough, since I only completed it in the GBA era and thus had to figure out myself that GBA hardware doesn't let you trade on GBC games.
I plan on doing it in XY as well. At least the regional dex shouldn't be hard if I just catch everything on every route before moving on. A check list like in BW2 would be really nice.
I recently finished the National dex in Black 2. I was able to get every pokemon from all of the games I owned, except the Glameow line. I had to trade for it. I find it pretty funny and odd how it worked out like that.