If you haven't already read my post about chance versus choice, you'll want to start there. Players don't want to keep playing the same game with the same outcome. As humans we crave entropy. Whenever a game slides too far toward the strategy end of the spectrum, the outcome becomes predetermined–the player with the best strategy will (nearly) always win. As game developers we need ways to mitigate this inevitability.
Bowling is the worst. The difference between knocking down nine pins instead of all ten is devastating. After three frames of knocking down all ten, your score could be as high as 60. After three frames of knocking down nine, your top score would be 27. When casually bowling with friends, those who are just a little better continue to get compounding rewards. It's a strange way of making the rich richer and it leads to predetermined outcomes and, more importantly, it dramatically lowers the losing party's incentive to finish the game. When we develop games we call this the Bowling Effect.
Monopoly, when played incorrectly with money in Free Parking, suffers from this same phenomenon. With a few lucky rolls, the player who rakes in the accumulated cash immediately takes the lead and then has power to widen the gap very quickly through the purchase of houses and hotels. After that point in the game those who are left behind become disengaged and can't wait for the game to end. This isn't how gaming should be. (I acknowledge that Monopoly's official rules don't apportion any money on the Free Parking space and the game isn't terrible when played correctly).
Board games that reward the player who already has the most always end up being short-lived. Once the pattern is discovered the loser doesn't want to play anymore.
Mario Kart, while not a board game at all, has a method of solving this problem. The game mechanic is called "catch-up". When we create new games we call it the Mario Kart Effect. When you play Mario Kart and end up in first place, you won't get the best items. Typically you'll get only bananas that you can drop behind you hoping to block the path of an opponent. However, when you fall behind even just a little, you start to collect more powerful items like shells and mushrooms that help you catch up. If you fall all the way to the back of the pack you'll get the strongest items like lightning bolts, Bullet Bills and other crazy things to help you get back into the race. I recognize that many people are sore winners and like to rub the victory in others' faces, but for the rest of us this effect is ideal. By giving the losing party a leg up they remain engaged and incentivized to finish the game. Applying this mechanic to your board games is a great plan if you want your game to continue to be played long after the newness wears off.
So here are some tips. First of all, be extremely judicious about giving a bonus or reward to the player who finishes something first. Typically, there's already an intrinsic benefit to being first and you don't want to tip the balance in favor of the person already winning. Second, as you're balancing your game, pay attention to whether the players starting out at the bottom ever end up winning. If there's no surprise ending or change to the leaderboard that occurs during the game you may just be bowling.