I have done the P90X, too long, too boring, too much was left up to me.
I've been a Crossfitter for over 3 years now, it's the only thing I've found that holds my interest. Like was mentioned above, it constantly changes. We have a Crossfit gym where we have all the equipment, can do Olympic lifts, sled pull, you name it.
If you are just looking to lose weight, working out is only a small part of it. You've got to eat good, clean, healthy food. Eliminate foods with processed sugar and eat very litte breads and you'll see a drastic diference.
Whatever you do, make sure that you do it correctly. Getting hurt will hamper your road to fitness.