The highest balance between popular and profitable is definitely Loli. The harem tag tend to just follow everything around.
But as stated, if you can't make your game with passion and dedication, you are going to have a very short life as a developer. It will lead to you making a substandard product that and if people know you are doing it for the money, they won't have the trust that you will even stick around unless you make bank.
Some games hit it off instantly, but as a general statement, a good game might start making a moderate amount 6 months after release. You will probably have to front load about 3 months worth of design and basic work to hit release as well. It might become actually able to support you within 2 years after release.
So in short the first thing you will need if you want to make money off this is another job to support you, the second thing you need is the drive to work for probably years and you might be able to support yourself. Keep in mind that is still only a possibility that you are even making minimum wage at this point. If you think these numbers are pessimistic, they aren't, unless you are putting out something truly, fantastically special, this is in all likelihood the best case scenario.
If you don't make what you're making with passion, you will never be able to deal with the ups and downs of being a developer and in all you will probably not make a game people will be interested in paying for.