Depends.
Heavy graphics/gaming best an i5/i7 with a decent video card, with light gaming I would lean towards an i5 with integrated HD graphics that can play most games and provide decent graphics performance.
You can always use an i5 with integrated graphics and later add a Video card of course.
Performance difference between i5/i7 not huge for much of the line until you get into megabucks.
That said I use a Quad Core 8-thread 4th Gen i7 at work and much of the time all threads are at 100% (heavy Java VM execution) and fan is active ))