I've been learning English through video-games since first year as a university student. Fallout, Planescape Torment, Shenmue, KOTOR, Vampire: the Masquerade - Bloodlines, Neverwinter Nights, Mass Effect, Dreamfall, Dragon Age, numerous shooters and strategy games.
It helped a lot, really, although my vocabulary now consists of quite specific words - I know weapons, ships, engineering, components, computers, command structure of US military, and how the jedi speak, but sometimes have difficulty with simplest everyday things.