While its true that some pokemon get WAY too much attention (Raichu, since DP, has been printed at least 7 times. Kangaskhan, since Base Set, has been printed at most 7 times), I think that the pokes seen in the top are quite differing. Lets make a list of some of the top decks of the past while, shall we?
Sableye, Garchomp, Luxray, Blaziken, Gengar, Nidoqueen, Torterra, Flygon, Gardevoir, Gallade, Regigigas, Machamp, Donphan, Kingdra, Beedrill, Magmortar, Honchkrow, Dialga, Palkia, Azelf, Uxie, Mespirit, Metagross, Dragonite, Banette, Jolteon, Absol, Dusknoir, Infernape, Delcatty, Lucario, Blissey, Empoleon, Bronzong, Toxicroak, Scizor, Steelix, Lugia, Blastoise, Manectric, Mew, Jumpluff, Gyarados.....thats 43 pokes already thats been used in winning decks over the past few years, and im sure I missed quite a few. I mean I'm not even counting stuff like Claydol, Raikou/Entei, Skuntank G....