Would this PC be good for gaming?

My Pc is here: http://pcpartpicker.com/p/30ovk

I think i got all the parts right, and I already own the RAM,Case,Case fans, thermal paste, and the HDD.

What do you think?

Yes that is a very good well balanced system. I would get an aftermarket CPU cooler though to keep that i5 cool in the small mITX case you have. It would also allow you to overclock it too. 

This is just a personal thing too, but I would go with Windows 8.1. It is faster and more secure than Win 7 and will have a longer service life. Some games perform better on Windows 8 as well.