Notice I did not say "good" I said "fairly decent".
However, Intel has made very good progress since their GMA 4500 integrated graphic core in only a few years; due to Apple's prodding for better integrated graphics performance. The Intel HD 4000 is basically equal to to the desktop Radeon HD 5550 and the integrated Radeon HD 7660g is basically equivalent to a desktop Radeon HD 5570. Yeah, sure, the Radeon HD 7660g does perform better than the Intel HD 4000. However, how long has AMD/ATI been producing integrated graphic cores that are capable of playing games compared to Intel?
Interestingly enough, the Intel HD 4000 is overall more powerful than the nVidia GT 610m. The one thing that holds back the performance of the Intel HD Family IGP is driver support. If they can improve optimization of their drivers, then Intel does not have to rely overwhelming on better hardware to improve performance.
Earlier in the year, there was an article about how the "Intel HD 5000" (not official name yet) was going to be a graphics core "monster" because it is going to have up to 20 shaders in the laptop CPU (GT3). Not sure how many shaders the desktop versions will be (GT1 & GT2), perhaps they will have 16 shaders; whatever. But at least for the release of Haswell, the shaders are going to be used more for lowering power consumption rather than a large increase in performance. While the "Intel HD 5000" is going to be more powerful than the Intel HD 4000 (I'm guessing around 15%, maybe 20%... maybe...), the clockspeeds are going to be lower to reduce power consumption. So the "Intel HD 5000" will likely be slower than the Radeon HD 7660g.
This should change when Intel releases Broadwell in 2014. With the die shrink down to 14mn, Intel should be able to maintain low power consumption while increasing performance dramatically. CPU core performance aside, the "Intel HD 6000" (for lack of a better name) might see an average of 35% increase in performance over the "Intel HD 5000"; similar to going from Sandy Bridge to Ivy Bridge.