I recommend the i3-3210 of the two.
I couldn't find any great reviews, though I did find THIS:
http://www.legitreviews.com/intel-pentium-g3220-processor-review_137016/10
However, there simply aren't enough games in the above review. Most weren't hardly bottlenecked at all in this review. This one was, but other games could be even worse.
HT:
Actually many games CAN use hyperthreading, and NO they don't have to be specifically coded to use it. From the point of view of Windows it's basically a 4-core CPU. I've even TESTED this myself by disabling TWO cores then testing a few games with and without HT and some did better with HT though I forget the results.
HT can add up to about 30% maximum improvement compared to being off but you likely wouldn't see that in most games. It would probably be somewhere between 0% and 20%.
Unfortunately, I really can't say how the CPU's compare. It's really just an educated guess so I can't be certain which CPU would perform better.
*My guess is the G3220 would perform better in games that aren't well threaded, and the i3-3210 would be best in better threaded games.
On average, I would bet on the i3-3210 as the best choice.