My suggestion is Galaxy S5. This phone have great 16MP cam with 4k video recording. It also comes in great colors and what I like is its finger print scanner. Just imagine you are somewhere at work and you unlock phone with your finger like a boss! This phone is water proof up to one meter and 30 minutes. You can take underwater pictures, use in shower or capture your self a picture in water ^.^. Its quad core processor is intensive enough to handle any heavy apps, multi windows. GPU is also powerful that you can play all games on that phone. It is also installed with latest kitkat OS. Heart rate sensor is also a cool feature to have in phone. Beside it has many other sensors that include, proximity, accelerometer, gyro, compass, air pressure and others too I forgot. Not necessary but if you can afford galaxy gear 2 watch it would be a cool combination of smart watch + smartphone!
The best phone depends on what you do with it.
If you like a feature phone then the gs5.
If simplicity is your thing then lg g3
If gaming then sony experia z2/3 as it is compatible with playstation 3/4
Iphone only if you are heavily invested in their eco system