This is a common question, and the answer is - it depends.
Taste is subjective.
The best cruise line for you might not be the best line for someone else because everyone has different priorities, interests, etc. You'll be spending quite a bit of money so it will be worth it. The good news is that you probably will enjoy the cruise on any line - they all do a good job. But if you can zero in on one which may be best for you, you may even have a better time.