Great Movies

I often wonder why critics usually give bad reviews for blockbuster films. For example, movie reviews of 300 came in the range from mediorcre to "it looks like a video game". People will say the movie wasn't historically accurate or the plotline was horrendous. However, the film came to generate seventy million dollars on the opening weekend. Other movies such as "Crash", a movie about drug trafficking, garner many praises (and the Oscar award for best picture) but fail to earn money in the box office. I guess what I'm trying to say is, "Is the point of the movie to teach people issues, or to entertain them?) Going back to the Oscar awards, movies that win this usually don't get a lot of revenue or attention. Quick, what movies took home the major Oscars? Hard to get off the top of the head, right? (I think it was The Departed that won best film.) What if I asked another question such as, "Name the top movies of the past year"? Dead Man's Chest and 300 would be in many of the replies. While it would be great to have a movie be entertaining and teach lessons in life, I believe a movie's first goal is to make the experience of going to the theatre enjoyable. Movies are suppose to take me away from reality and put me in a world where I can be in suspense, horrified, or in the action. I am not a critic. I cannot see the nuances of a movie that can seperate great acting from good acting and the like, but I can tell whether I was thoroughly please by the film as a whole. That's my take on it, but what do you think a great movie should be like?