Between the Intel's the i3-2100 is better than the G620 in a lot of benches.
As seen here....http://www.anandtech.com/bench/Product/406?vs=289#
And between the i3-2100 the closest comparison I could find was the A6-3650 which is better than the 3500.
The i3-2100 still happens to be scoring better than the 3650.http://www.anandtech.com/bench/Product/403?vs=289#
So the first one , best out of the three happens to be the i3-2100
Between the G620 and the A6 we find a very close but never the least Intel lead over the AMD one in certain benches.http://www.anandtech.com/bench/Product/403?vs=406#
So over all depending on what exactly you'd like to use the processor for, the apps you're going to be using would make it more definitive.
So in order of Best to not the Best
1. Intel i3-2100
2. Intel Pentium G620
3. AMD A6-3500