This weekend brings the year's first major sci-fi release to the multiplex, and audiences should be flocking to it after weeks of tepid rom-coms and half-baked horror flicks. "I Am Number Four," though weakly reviewed, stands to win the top spot at the box office over the four-day holiday. "Unknown" and "Big Mommas: Like Father, Like Son," alas, don't stand a chance. Which one is right for you? Or, perhaps, is now the time to avoid the new offerings and hit the Oscar faves ahead of next weekend's Academy Awards? Check out what the critics are saying about "I Am Number Four"...