#1 - would be nicer if the water spray from the merlion is not pouring out of the frame. Meaning a wider view may work better here.
#2 - See 1 above. A landscape orientation will work better here.
#3 - horizon tilted to the left.
#4 - nice colors but horizon tilted to the right which spoils the picture.
#5 - A little bland. If you move further down the walkway on the dam at Upper pierce, and capture where the sun is setting, it will be much better. And with such overcast clouds, maybe you can try a 16:9 crop instead.
In landscape pictures, the horizon is very important. You have to keep it level. If not level in-camera, you have to fix it in PP. Good try though.