I went to a Senior Health Fair last week where I talked with about 200 senior citizens about my Zumba® Gold classes. I could tell almost right away which ones exercised on a regular basis and which ones didn't. I verified my hunches with questions and I was always right. My observations were based on their posture, the brightness of their face and even the way they spoke. Those who exercised regularly smiled more, moved with greater confidence, and had a certain strength to the sound of their voice. It was a huge testament to me of the importance of exercise throughout life--and that exercise is not just about losing or maintaining weight. It adds quality to your life!
I recently read a statement that said the consistency of your workouts is more important than the intensity. (Wish I could find it again).
This means a couple of things to me. Like I've said before, you should focus on ENJOYING Zumba class®, rather than focus on doing the moves "correctly" or trying too hard to burn lots of calories. Enjoy it and you'll come again. Consistency will happen.
Also, if you aren't quite feeling up to the workout on a particular day, it is better to come and give it a light effort rather than no effort at all [but if you're sick, rest].
What is the best exercise? The one you LIKE! And it can be different everyday. Try something new. Pilates, running, Yoga, Boot Camp, swimming, Spin, Tai Chi, Zumba®, basketball, weight training.