The G2 and S4 are capable of taking very good pics. My G2 had some issues with low light situations and moving objects. Fixed these issues by installing Xdabebb's camera mod. Now it takes great pics and has HDR video mode.
The G2 also has low headphone and speaker volume. Using a volume mod or Viper4Android can significantly increase the volume. I installed V4A since it has good EQ, volume booster, and other nice sound settings.
Once those issues are addressed, I think the G2 is a better phone than the S4. It has knock on/off, no lag at all, significantly better battery life (6-8 hrs. Screen time) , charges faster, bigger screen and innovative back buttons.
The main reasons to buy the S4 are the SD slot, removable battery, and if you happen to prefer Samsung's AMOLED over the IPS LCD on the G2.
Sent from my Xposed LG-G2 using Tapatalk