That answer entails too many scenarios, it depends on the game, resolution and detail settings. Some games utilize a quad core, some games don't utilize quad cores but at the same time do indeed show the i3 performing less capably than i5s. And some games like Skyrim put some of the work on the CPU that would normally be done by the GPU.
I would say as a generality, I probably would consider a video card more powerful than a 7850 or 560 TI to be "unbalanced" with an i3. Thats my opinion however.
Okay, thank you for the advice!
It all depends on how much 'bottle neck' is too much for you. You can run any size card you like. The faster the card, the faster the frame rate will be.