I believe this question, the related question, and all the answers I have read are missing the point a game ought to have. Where the game is not almost exclusively chance (those that are, are irrelevant to the question at hand), the point really is not if one wins or loses -- the point is to learn strategies. The type of strategy is dependent upon the nature of the game, of course.
My daughter is 14 now. I have not once in her entire life let her win a single game. I have, however, tried to educate her about the nature of performing better at each particular game. Sometimes it was in the form of questions (e.g. "Oh, why did you do that?" ... "Hmm... I can see why that seems good, but did you notice...?") while other times it was in the form of laying my cards on the table (e.g. "So, I am thinking that if I do ... then it'll be harder for anyone [importantly, not naming her] to do ... and will help me.) My personal preference is to make any educational component indirect or else the game will seem less game like and more like a classroom, defeating the "point from her perspective."
In addition to the other answers which show a balance in being a good winner and a good non-winner, this method serves to educate.
To my supreme delight, her creative mind has very often come up with quite ingenious alternative methods... some of which do very well and others demonstrate why they are not the best choice. The consequence of such thinking is that "the box" is not her confinement -- her imagination is.
Consider also, as appropriate, online games where you and your child can form a team against AI opponents. This allows you to brainstorm strategies and see how well they perform without competition between you and your child. My daughter prefers this over her-vs-I at this time in life.
Win or lose, did we learn anything useful? Is that not what the conclusion to any game of strategy should be... a question about personal growth?
Side Note: Since the game is about learning, imo, I have let her change a move after chatting with her about it... enforcing the game rules is not the point. If she understands the consequences and chooses an alternative, why not let her make a change?
Final Side Note: Yes, she has won games with me on her own merit and was elated, chatting about it for days -- she trusted that I didn't let her win, but that she earned it, and that made the "win" all that much better. Not only was she elated, but I was proud to see her do so well!