Is weight watchers the most successful program?

No. The best program is the one that you can stick with and change behavior. Tips: make half your meal vegetables and fruits. Go for variety. And keep in mind that potatoes and french fries dont count. choose whole grains & limit refined grains. pick the healthiest sources of protein. Drink lots of water. Stay active.
Best commercial plan. I've seen thousands of patients over many years, weight watchers is the most consistent with losing weight and keeping it off, teaches you to make better choices. People who dont lose weight are not being honest with themselves, and not keeping up with their points.