To answer the question and address some points others have made - from my perspective the comments are great to tell someone they've done something impressive for the time. The star ratings I try to keep more objective to facilitate comparisons. I don't find that very easy though as whilst we all have the same constraint of time, it's often comparing apples with oranges. Games developed with different amounts of pre-made elements and teams all dramatically alter the ability for someone to scope and adapt to circumstances, and in the case of teams can dramatically alter the man hours available. To ignore these things entirely would be for game jams to tend away from having individual developers - so I take the approach that where I am unsure if I should give a game, say, a 4 or 5 in a category then I will tend to give individual developers the benefit of the doubt.