There are many smartphones with the highest megapixel camera out there but you need to let everyone know which OS will you choose for your smartphone, iOS or Android or others? so it will be easier to advise you.
I think the oppo f7 is the best camera phone right now, with 25 megapixels, imagine that, but I don't know the quality of that phone. If you are just looking for the camera, well, that's enough I think. and it's really good for selfie, and based on the reviews, the oppo smart phone really develop their camera, and wanted to become popular on their camera.
Girls are more inclined to taking selfie pictures with their phones with the use of selfie stick. Now, such girls or women would prefer phones that comes with higher front camera megapixel in order to have a better pictures or photos experience using their phones for such purposes.
So, having pointed that out, it's only one phone that comes to mind if it's for the purpose of getting a better selfie pictures. The phone in question is Tecno Camon CX. It comes with 24 front camera megapixel.
When it's about Phone camera Oppo phone's are one of the best. There camera capture are clean. Like there latest smartphone Oppo F7 with 25mp. But huawei have lunch one of their best product which I think the best smartphone by far and they name it huawei P20. It,s price are not a joke but It's pack with a high-end specs.
I'd like to recommend Nokia Lumia 1020 boasts 41MP (38MP), I think this is the only phone that has the highest megapixel and has the best price over 400USD. I also recommend Sony Xperia XZ Premium offers 19MP, it's affordable and has a good camera quality.
If you are from the side of the World that I am from and you do not know of Tecno you are literally in your own world. Currently the camon wave is irrestistble and their cameras are a huge reason for that.
If you want high megapixel camera, you can choose from either OPPO or VIVO phones. For OPPO, their best not so cheap no so expensive phone is the OPPO F7 which has a 25 megapixel front cam and a 16 megapixel back cam. While VIVO has the VIVO V9 which has the 24 megapixel front cam and a dual camera back with 16megapixels.