Considering that many game sequels tend to share only certain gameplay and style elements without continuing the same story or including the same characters, I can't think of any good games that it would necessarily hurt to make a sequel. Much easier to think of games I wish would get a sequel. If we're talking about actually continuing the story, well, most Final Fantasy games should not have sequels, but unfortunately far too many already do. I'll say FFVI. I think they haven't spoiled that with an FFVI-2 yet.