Since I post reviews of movies, I think it's important that I also mention my pet peeves or things that are required for me to like a movie. In some cases, of course, personal taste/interests make me like a film more than I probably should. Case in point, I loved Watchmen but a lot of that had to do with the fact that it hit on things that I am interested in. I could absolutely see why others would find the film to be a complete bore. Anyway, I thought I'd start compiling a list of the things that I basically need to enjoy a movie.

As a savvy/jaded filmgoer, I go into a movie pretty much knowing one thing: the main character is not going to die and if by some crazy twist, he/she does die, it's not going to be until the final scene or so. For that reason, I really don't get that fired up or nervous about a scene in which the only threat is to the main character's life. If I'm sitting in a theater and we're 40 minutes into a film, I know that the lead character isn't going to die and any threat to his/her life isn't that daunting. If the conclusion is obvious, there isn't any tension.
Now, there are three ways around this issue.

1."How" Not "If": There's one movie this summer that is supposedly a white knuckle thriller but all of the action scenes only focused on IF the main character would make it. Since you know he isn't going to die midway through the film, I was just never on the edge of my seat. The fact of the matter is that for a scene to really work for me personally, the focus needs to be on HOW the person is going to survive not IF he is going to live.
James Bond is the king of this. Everyone knows that Bond isn't going to die, but he always has some suave move or cool gadget to help him get out of his scrapes. Whenever Jason Bourne was in trouble, you didn't think "Is this the end of Jason Bourne?", you sat up and wondered, "How's he going to fight his way out of this one?!" Die Hard is another example of this. While survival was obviously the main goal, getting the attention of the police and finding a way to end the hostage situation were equally important goals. Even if you realized that Bruce Willis wasn't going to catch a bullet midway through the movie, it's interesting to watch the bad guys (and sometimes the good guys) thwart his plans to save the day.

2. The Predator Ensemble:: Just because the lead character isn't going to die doesn't mean that everyone has to live. You often can get around a lead character's inevitable escapes by adding side characters who may or may not make it. I can still follow the main character's heroics but then worry about the supporting cast's safety. This is why horror films are scary; there are usually a bevy of supporting actors, all of whom could eat it at any second. Scenes in which the lead is getting threatened are usually the least frightening of the film. You're just watching a chase that you know is going to end with the good guy/girl getting away.
Other great examples of this are Predator, Alien, Aliens, and Band of Brothers. I hate to include Band of Brothers because it's a true story and real lives were lost but it's basically the best example of how films should be written.
That being said, you have to establish these supporting characters early on and get the audience to care about them. You can't have the characters who die be nobodies ala Star Trek's infamous Red Shirts. Also, you can't do the Lost: Season 2 trick of just adding new characters and then killing them off. It barely worked in a TV series and it definitely doesn't work in films. Unfortunately, this is happening more and more often in films and it's getting to the point that whenever you see a new character pop up (especially if it's a known actor), you can be pretty sure that they are going to get popped in the near future.
Then, of course, there's the cardinal sin that "Heroes" has committed: Death is Not Forever. So many people have died and come back in that show that nobody cares if somebody dies because they realize that they are probably just going to come back.

3. Kill The Hero: This rarely happens and I'm not sure if I can remember the last time I've seen it but killing the leading man is always an option, especially in an ensemble film. Now I don't mean the now cliche "Scream" trick of putting a famous face in the beginning of the film and killing her to make people think anyone is at risk. By now, people get that gimmick already. But it really seems like it is about time for a leading man to get it in a movie and then have the supporting members have to step up and save the day.

Long story short, if the main driving element of a film is "Will the good guys win?!" or "Will the hero survive?!", I'm going to be bored to tears. Everyone knows the day is going to be saved, HOW the day is saved is what is entertaining.