Kakulin, I'm not sure mastering English can be slimmed down to just watching TV and playing videogames. I'll admit that being a gamer myself, I do know how they can play an important role in learning vocabulary. Watching TV also helps, I do not deny that. Furthermore, browsing the Internet on a regular basis and taking part in online conversations on a regular basis (forums, IM, and so on) also helps. It's very easy to be exposed to English, especially from a technological standpoint.
However, while the forementioned learning methods are genuinely useful, they will only lead you to achieve a standard level of written English. There's two issues with this:
1) You are leaving out spoken English -- the hardest part of the English language;
2) To go beyond a standard level, you will need at one point or another to read books in English, use an English dictionary --something further pertaining to the area of the written aspect of English that will solidify your lexicon (then again, it really depends on what you aim to achieve).
There's also another problem. Many people claim to know English. I see it often in my Spanish-speaking country. Our middle school and high schools teach English as a secondary language, and people learn it through several years. These people, upon finishing high school, think they know English. I have lived in the states for a short while (2 years and a half), and I have worked on a job that required me to speak to americans, and I can tell you, these people don't know English. And while your posts seem to be intelligible, I am rather skeptical when a non-native easily proclaims his seemingly good level of overall English.
The more I learnt English, the more I realized I didn't know, and the more I realized how much those around me didn't know.