Epic's reveal of the Unreal Engine 4 feature set, as well as some of the company's previous statements on their goals for the new engine highlight some of the isseus that studios are running into creating games with the visual quality standards that gamers have come to expect.
The manpower and computational requirements for building a AAA 3D game have become enormous. For a character alone, a high poly and low poly mesh must be created, textures must be painted and tweaked, motion must be captured from live actors and finessed by skilled animators, behaviors of the character must be created by programmers, and the list goes on.
One of the most frustrating elements of development isn't the time taken working on a feature, but the time that computers spend calculating that mean the developer cannot continue to work. There are two places the team is hardest by this problem.
First, compiling/building the game: When a programmer makes a change, it requires the executable file of the game to be recompiled, this takes time, especially when developing for console, where the updated code must be transferred to the console for testing. Programmer time is valuable, and if they are unable to continue to work, those minutes here and there add up and cost the company thousands of dollars very quickly.
Second, level design. Since the days of the original Unreal, colored lighting has been in 3D games (for better or worse, in some cases). While there was some use of dynamic lighting, primarily, all the scenery that appears to be lit was pre-calculated before the game was ever put to retail. Dynamic lighting is extremely expensive on the computational side, and that cost has to go somewhere. In the language of the Unreal Engine, the LD "Builds Lighting" and then goes off to take a break. The process of calculating lighting in earlier iterations of the engine was extremely time-consuming, and it became prohibitive to do a full-quality lighting build in recent years as the quality bar ratcheted up to meet hardware capabilities.
On Unreal Engine 3, Epic implemented Swarm, a feature that allows the lighting process to be distributed among multiple computers in a render farm, returning a good amount of time back to the LDs, but at the very tangible cost of expensive server hardware, or using the resources on coworkers' machines. (Note: this can also be achieved with cheap hardware laying around for users of the free UDK, but corporate users are less likely to risk their productivity on low-end hardware.)
Unity uses Autodesk's Beast system for global illumination lighting calculations, although their system does not currently support network distributed rendering.
Other solutions are out there as well for current-generation projects.
Epic's strategy of next-generation systems relying on a purely-dynamic global illumination lighting solution is ambitious - and likely the shape of things to come as Crytek, Unity, and other 3D engine and middleware providers bring their focus on the next wave of consumer gaming technology.