Boss Sam, thank you for the good lesson.
I always want to see the pictures from my big TV screen say 45 inch and above or from my Macbook pro.
if that is the case, is MP still important to me? please guide me
If you're viewing on a TV screen the limitation will be the resolution of your TV set not the image. What sort of TV do you have?
In addition the size of the TV screen is not the measure of the resolution. For example a FULL HDTV has a resolution of 1920 x 1080. This is the same regardless of whether the screen in 32" or 60".
If you have an HDTV, as long as the image you are showing has a resolution of 1920 x 1080 or greater there will be absolutely no degradation of the image. This means that you don't need anything greater than a 3 MP camera.
Read the article at http://www.kenrockwell.com/tech/mpmyth.htm