I think what usually happens to me is that I play so much of a character in a previous game that I need to change characters. My main in Smash 64 is Luigi, and is one of my best characters in every other installment. Same thing with DK and Jigglypuff. But in Melee I play as Mr. G&W, Roy, and Falco more. Then in Brawl I play them less and so on.
Same thing happens to me in Crusade, where I barely play as any of the veterans and only play as newcomers.