Its nearly impossible to say which one is better. Performance doesn't solely depend on a processor, you have to have matching mother board, RAM, HDD etc. Some configuration match perfectly and some don't, thats why you may find two computers having same processors providing different performance. Both the companies make very good processors and its best to use the recommended accessories with them; then only you can get the best performance.
Just like it was said many times...
AMD has higher frequencies of their CPU's, can be more overclocked, has more cores and they are cheaper. And there is a reason for that.
Lets take Intel Core i5 4670K VS AMD FX 8350
Intel has 4 cores with base clock at 3.4 GHz and can be overclocked
AMD has 8 cores with base clock at 4 GHz and can be overclocked
So, logically, by the numbers above someone would say that AMD is much better. But it isn't. Intel's single core is much stronger than AMD's. So it's like you have two warriors, one has 8 swords made of quality wood and another has 4 swords made of quality steel. On who would you bet?
In this case even AMD has more cores (would easily manage multithreaded apps, or more apps at once) it would have only 2% higher performance compared to the Intel who has double less cores.
And in single threaded apps Intel is 53% faster.
Also power consumption is much much better with Intel's CPU's.
And many other factors like cache, manufacturing process, performance per watt, instructions per transistor, etc etc
Not all the games or apps are optimized to run multithreaded with more than 3 or 4 threads (or cores), today.
Do not get me wrong. Both CPUs are just fine and really powerful.
But if you ask who is better, Intel would be better, much or less.