Is it normal for this to happen?

I have my Samsung GS2 and if i charge it on the wall with the stock cable it charges pretty fast like 15% in about 10 minutes or so,but if i use the same cable and try to charge on my pc it takes at least 4-5 times as long to charge.

Is that normal?

Yes.

I believe ASUS made a port that charges apple products instantly. I know the GS2 isn't Apple. I'm merely stating that you should experience different variations with various types of port/ technology.

USB doesn't have the same kind of power capability as a USB wall jack.

But Berserker is right, some Asus boards have a USB3 port that can be set to allow fast charging of USB devices.  Also, if you're running a custom ROM, I know that Franco Kernel has a setting that allows faster USB charging than what is usually allowed.  It puts it pretty close to wall jack speeds through any USB.