It actually fits very well! As the original resolution of the game is so low, the buttons are really nicely sized for use with a smartphone
I've played through it once on my Xperia ZL (5" display, S5 has 5,1", so it's only slightly larger) and thought the touch controls fit the game like a glove!
It'd only be problematic if you intended to use higher resolution, as then the buttons are equally smaller, but I found that unsuitable on the phone. So, go for it, it's worth it