You have a first idea that come to your mind. then you start entertaining other possibilities. maybe maybe and maybe.
there is the one first idea, and the myriad of alternative ideas. who is better? (on average)
The first idea that comes to mind, compared to every single other idea, is generally better. Not better than all the ideas. But better than the next one, or if compared to one idea of the bunch chosen randomely.
the reason is that what comes first to mind is not coming first for no reason. the system is usually bringing the seemingly best idea first, and every additional idea is on average of lower quality.
Now one of the additional million ideas, is probably better tahn the first one. But this is only this idea that is the best of all the rest.
So if you select the best idea of all the all the newer ideas, you can get a much better idea than the first. But the average idea is worse.
PS> related to stupid openmindedness post above