Unreal Engine 3 Engine

Unreal Engine 3, released in the mid-2000s, introduced normal mapping and more physically grounded lighting that became the visual standard for a whole generation of games (Gears of War among them). For MMOs, the engine marked a clear step up in character and environment detail over its predecessor — which is why studios moving on from UE2 toward more visually ambitious projects picked it up, including NCsoft's Blade & Soul.