APU quadcore A8 vs intel core i5,i7 processors

I would say start hunting for benchmarks of each cpu :)

google.com

i5 or i7 hands down. AMD cant compete with either at competative level.

mobile gpus tend to be poor in anything other than ones aimed at "gaming" .

any of the processors mentioned would be fine for gaming, however the apu which itself contains a graphics core will lag behind the intel based ones with a dedicated card.

i5 will be ample i7 will give it beans with some to spare.

If you are talking about a laptop processor the i7 will dominate the rest including the i5 because the laptop i7 has 4 cores vs the i5s 2. The amd has four but amds cpus to not perform as well as intels cpus.
If you are talking about a desktop I would highly recommend not getting an a8 look into the 6300 or 8350 if you want a cheaper cpu for a desktop and dont want a cheaper intel cpu like an i3.

I suppose it all depends on the games you want to play. When it comes to high end gaming i have never been impressed with laptops. They never preform like desktops. With that said im sure there are some fine laptops that can game quite decently.
You can get a powerful cpu but i have found that the most powerful cpu never compares to a good graphics card when it comes to gaming. I have friends that still use old pentium cpu's but have awsome graphics cards and I wonder were i went wrong with my 6 core AMD. :)
Desktops have pci and pcie slots for the more powerful graphics cards, were as laptops are built more compact and usually have on board graphics. Also I have found in many cases it is cheaper to build a desktop than a laptop anyway. Not only do you save some $$$ but you feel good about your custom built piece of art.

If you are going to play more simple games like those on Facebook than i would say a laptop would be fine. Like I said, it's all about what your playing.