Played both, completed FNAF, stuck on 10/20 mode on FNAF 2. Its more tedious than it is scary now.
Honestly, the original was my definite favourite of the two. I enjoyed it despite the amount of times it made me metaphorically shit bricks. The second was just too predictable and although finding the Withered models in the back room made me wonder how much more 'fun' that would make it, I still preferred the simplicity of the original.