Doing a quick 5-min mock-up using Chrome's dev editor, I came up with a format like this:
A: The movie's score from the critics.
Other thoughts include a x%/y% where x = critic sore and y = audience score
B: The movie's title
C: The movie's poster image that is on their page.
D: The icon of whether or not it is 'rotten' or 'fresh'
E: The critic consensus (if there is one)
In order to properly OneBox the link should be like as follows:
For my example, Dark Knight, the link is:
While RottenTomatoes itself isn't a hugely useful site; people do use their reviews as a basis. On top of this, we could also implement something for IMDB in a similar fashion, replacing the RT rating with IMDB's overall rating.