We make time to ideate... we call that a brainstorm; these can last an hour or more. Yet, when it comes to judging the output of a brainstorm we tend to allocate a few minutes at the end. It's not enough time to get the most value from the ideas in front of you. Allow at least the same amount of time you did for the brainstorm (if not longer) with a smaller group of people.
When you started the brainstorm your goal was to find an amazing idea. Well... there's a big pile of possibilities in front of you after a brainstorm, don't rush things and miss something amazing.