Final Fantasy XII >>>>> Final Fantasy X
Final Fantasy VI and IX >>>>>Final Fantasy VII
I agree with the first one if talking about the original version of XII released on PS2. I disagree with the second opinion but I don't even think its that unpopular, at least among fans of the franchise, I know that in terms of overall popularity, VII is the favourite but I don't think there is a more popular game to prefer than VI or IX (IX being the highest rated FF game on metacritic). If you preferred FFII or XI then I think that would be an unpopular opinion.