I would say that whichever exercise, you, personally, can endure for the longest periods of time would be the best. The key to losing weight in exercise is to keep the heart rate up for longer and longer amounts of time. So if you can walk for longer than you can run do that. If you can bike longer than you can walk or run do that. Bicycling is also lower impact on the knees if that is a concern
sex
running and walking for 20 min is still the best weight reducing, calorie burning and cardiovascular exercise. although this type of exercise can cause injury to your knees and feet for it has impact. faster the pace, greater the impact.cycling on the otherhand is more enjoyable and low impact exercise. but due to the magnified steps thanks to cogs, you need more pedalling and longer distances to have an effective fat and calorie burn. but it is both a good mental exercise (road scanning and alertness) and cardiovascular. it also gives you tone legs. you only have to deal with road elementsstationary bikes is the combined effect both cycling and jogging and but it is more boring and tiring.
Bicycling!