Best Romantic Vacation

IMO any place can be romantic with the right attitude, and in some cases, the right person. (Romantics generally can find beauty in everything, including the mundane.) So I would say that your choices are very wide open.

I see from your profile that you live in Singapore. Without knowing the time of year you are planning for the trip, how long you plan for the trip, your budget or your interests, my off-the-top recco is that you try someplace which has a different culture, as well as different geography and food. As you posted in Asia, Australia and New Zealand first come to mind. The Margaret River wine area of Australia would be lovely combined perhaps with a great city like Sydney or beaches on the gold coast. A driving tour of the South Island of New Zealand would also be a wonderful trip combined with some outdoor activities like hiking or canoeing. You can experience seasons like fall or even winter in either place.

Japan may be another option, you can see cherry blossoms or fall foliage and experience a quite different culture from SE Asia. There are traditional cities like Kyoto or Osaka, or go up to mountain areas for snow.

India would be another great place, go to. You can see the Taj Mahal, lovely beaches and/or the Himalaya areas. Time of year would be an issue here if you want to avoid heat or rain (and you really do want to avoid that). Sri Lanka would be perhaps easier to do if you only have a short amount of time.

If you can consider places outside of Asia, then Italy certainly has many beautiful places to consider, and there are many other countries in Europe that would fit a “romantic” bill. Or a safari in Africa would really be a great trip for an anniversary, IMO.

I would say that Bali would offer lots for an anniversary trip, but I wonder if you may already have been there on previous holidays.