I would recommend if you use a windows machine is Sony Vegas, as it is fairly cheaper that adobe or apple will charge. This will give you a more advanced look into video editing.
As I personal hate the new Final Cut X because it is very dumb down and limited, I would HIGHLY recommend saying away from it. Also with the time I have had with 6 & 7 that could be a way to go.
From there I would say Adobe Premiere (Windows & Mac) If your a College/University student you can get a huge discount from Adobe. This is what I have been using most the time I have been editing video.
Lastly for industry standard video editing AVID Media Composer which can set you back $2,000/£1,789 (Roughly) although this is top of the line, I found this to be so unstable when editing four hours worth of footage.
So I would say go with Vegas or Premiere, and stay clear of Final Cut X.