I would love to visit every planet possible, its like saying you want to visit every country. They all have their own extraordinary features and cool qualities that I want to explore and learn from. Obviously this would be extremely difficult having to sustain life by our own means on every planet but I believe in the near future we will have these capabilities of space faring civilizations.
And if I had to choose one after Mars I would go for Saturn, its awe inspiring form surrounded by a beautiful ring and on the contrary within its beauty lies extremely hot temperatures and high pressure with about 91% of Earth's gravity. We can't stand on it but flying through it and observing its beauty would feel amazing.