I have to agree with Toby. While FC may be more complicated than Movie Maker and iMovie, there is little in between that will get you what you want. You can try Final Cut Express, too. It's a little step down from Pro. A good app that has lots of controls and effects isn't going to be easy to use (like just pushing a few buttons and you have a movie. You need to take the time to learn the software of you will be stuck using a entry-level app that is easy to use. Once you start the learning process, you'll be surprised at how easy it is to pick up. If you really want to learn it, it'll go quickly and will be fun to do. You will need books and video tutorials.
Another video editing app that has a Mac version is Adobe Premiere. It is equally complicated but, in my opinion, a little better (for my uses). Adobe After Effects is not a video editor and is in fact more complicated since it is a different type of app (compositor) than a video editing app.
The best part about editing apps is that they are all basically the same. From the free and cheap ones to the pro-level ones, they all have the same basic layout and function. The difference is in the significant increase in the level of control and the features that are included.
Premiere pro, After Effects pro, Final Cut Pro, Avid Express pro