As said above, activity is better than sitting around. I am sure that there are other activities than biking. Swimming, hiking, just walking, aerobics, rowing, jogging, running, mountaineering, sport dancing, ball room dancing and ball games come to my mind and I am sure that I missed some.
Biking stands out for a number of reasons:
Anybody can do it who is reasonably mobile. Does not cost a fortune. Can be done anywhere. Your body will tolerate it longer than many other activities. It is outdoors but can be done indoors. Is easy on frail joints and has positive effect on damaged limbs.
Will it make you live longer and/or better? My opinion is that our body needs good foodstuff to keep healthy. Restricting that foodstuff to control weight gain is not good IMHO. Better is to exercise it off. Biking is one good way to do it.
We cannot do anything about genetics or unforeseeable disasters. Lets do that what we can do something about.