I'm sure there are good arguments for saying yes, but I firmly believe the answer is no. When I was a child, my father took pride in always being honest with me, and that included never letting me win at chess. He also told me that Santa wasn't real as soon as I learned who Santa was. When you treat kids like adults, I also think they like you and respect you more for it.

I never let my children win. What I did do, however, was make sure the games were at "their level"-- so that competition would be fair. ADjusting the rules ahead of time-- so that in Scrabble, for example, no word longer than 4 letters can be used, or that everyone starts out with the same number of properties in Monopoly can level the playing field. Children know when they are being patronized-- and letting them win can make them feel that you think they are not good enough to win on their own. False achievement does not build self-esteem.

Based on my personal experience, my answer is no, never let them win.
When I was a child, my father let me win sometimes at chess. When I realized it, I felt very upset, and asked him never let me win again. A time after I begun to win, claiming him "you are letting me to win again", he claimed "no" but I didn't believed him, that is, this fact caused me to loose confidence in me and in my father.

In return, my brother played giving me some advantage, like playing without some number of pieces, which was reduced with time, until we played with all the pieces, then when I won him, I felt happy and satisfied.
It goes without saying I preferred to play with my brother than with my father.
This is an excellent article about "Who Really Wins When You Let Your Kids Win?"

Regards!

First you should take a slight step back and work out why you are playing the game in the first place. Its unlikely that you are preparing for the world Monopoly championships where every win counts. Its not as if you NEED to win every time.

So why are you playing? Is it to teach little Jimmy how to play? Is it to spend a fun Sunday afternoon having fun with the family? In either case little Jimmy and the family aren't going to learn or have fun if you mercilessly crush them with your awesome gameplaying prowess. So for you to win (an achieve your objectives) you actually have to lose some of the games.

Now you shouldn't throw the game, but you don't need to play your A game either. If you're playing scrabble you may want to limit yourself to 5 letter words or less. You'll still have the challenge but it places a handicap on you.
If you're playing football then you don't go in tackling hard... if you're playing wrestling maybe you don't want to break a chair over little Jimmy's back....

No... you should play him the same way as you'd play a fun game against any other opponent. The point of you playing isn't to humiliate him, neither is it to let him walk all over you. Its so you BOTH can enjoy a game of tennis.

Its not a case of win or lose, its how you play the game. So play nice, play fair, and play for real. But remember you don't have to play exactly the same set of rules as the rest of the family.

I enjoy playing several simple games with my grandchildren which allow them a good chance of beating me fair and square. Even with something as basic as tic tac toe, Connect 4 or Fish, they sometimes clobber me and get the fun and satisfaction of winning. When we play games which are more skilled based like scrabble, I never lose on purpose and never "throw" the game; I think that giving them false achievements has no benefits. At the same time, I don't feel a need to clobber a 7 year old by playing with cutthroat tactics. When they get stuck for a word, or forget how to spell a word, I'll provide a clue.