As the title states, the distribution of planets has a strong input on how fun a game is.
One of several things will happen.
1) You will get screwed and not find a good quantity of colonizable worlds nearby, and your opponents will, then you get steamrolled.
2) You find a bunch of planets and they don't, you steamroll them.
3) Roughly equal numbers of planets will be found by all (or enough), and you have a good game.
Without cheating, it's hard to know before you are several hours into a game which situation reigns. It makes the game more about random luck than about choices.