I found two links on writing better reviews, for you critics out there. From Blogcritic, some tips like:

• What was your reaction when you finished the book? If it was powerfully positive or negative, that may be a good place to begin.

• What is the writer trying to accomplish? It's different for each genre: thrillers, romance, literary fiction, sci fi, etc. Does it work or not, and why? (Sometimes the idea is great but the mechanics are so bad that it has no power — see a list of the mechanics, below.)

• How does the writer handle dialogue? Does it flow easily, sounding natural, or is it stale with too many adverbs describing the characters mood. Remember the goal in fiction is to show not tell.

• What about how the artist describes surroundings and people. Again, too many adjectives and adverbs create weak writing. Is there too much needless description that just interferes with the narrative flow?

Then, Kristin Dreyer Kramer at Absolute Write gives you Review Writing Basics:

Movies:

Many of the same plot/character questions apply. Also think about:

Were the right actors chosen for the parts?

Was the dialogue natural and believable?

Did it keep your attention the whole time?

How were the effects? Lighting? Sound?