Generations of Intel HD graphics:
Intel GMA 4500HD < Intel GMA HD < Intel HD 2000 < Intel HD 3000 < Intel HD 4000 (yet to be released - Ivy Bridge).
The 4500HD can run Source games on low. GMA HD can run Borderlands on low without the artifacting and tearing suffered by the 4500HD. HD 2000 can run games on medium, but only comes in desktops. HD 3000 can reportedly run Crysis and Battlefield 2.
Many games are not optimised for Intel graphics, thus will NOT run with them. Some games require patches to run. Some games only require a certain model of Intel graphics minimum. Tell us which one you have (using CPU-Z or GPU-Z or whatever it was called) and we can tell you which category you fall into.