I think it's kind of hard to exercise just for health. Athletic goals work better. Try a couch to 5k program, see how many pushups you can do & train to do more, learn to stand on your hands or try to jump higher than you can now.

If you are asking what will help maintain your body for the long run, yoga is so good. In yoga classes I see people older than me in great shape still and able to move in every direction, flexible and strong.

If you want to look better, lifting cannot be beat. Add just a little lean mass and shape, small change but big improvement in looks.

But the most important advice is to do something you actually enjoy and will keep doing. Any sort of activity is much, much better than some ambitious plan you don't actually do. Try a lot of things, and after 6 weeks of consistent exercise of any sort, you will feel enough better that it will stick. You will sleep better too.