If we have two GameCube winners in a row, I'll probably avoid that system when choosing the nominees for the next poll. However, I won't make any apologies for opening the feature up to last-gen games, and they are obviously popular in the polls. I suspect that may be because these games are better known, still relatively easy to find at used game stores, and are easy to play on Wii.
And since it's causing some confusion, I will create a separate, permanent thread for people to nominate games. We have a pretty solid list of suggestions already, but new ones are always welcome.