Many industries (and I would dare to say, the whole history) develop in cycles. Game development is no exception. In the beginning (for some people this may be DOS era, for some even earlier, mainframe era) games were extremely simple and boring and were developed by individual programmers. Then games became more interesting with nicer animation and effect but still game development was more of a hobby. Gradually (and this has not happened overnight) game development became teamwork and ultimately the craft of companies which over time turned into large corporations.

Looking realistically, today it is (nearly) impossible for an individual to develop a successful commercial game. Yes true, you may come up with an excellent game concept but turning that into an actual game is virtually impossible. Even for small teams it is extremely difficult next to impossible to compete with large game development houses.

With the introduction of XNA, Microsoft is making an attempt to give individuals (but more realistically to small teams of 3-5 people) a chance to create games that may become commercially successful. This hypothesis is further strengthened by the fact that a game developed with XNA runs both on PC and on XBOX (and maybe on Linux in a near future).

But we should not forget that actual game development is just a starting point. Once a game is developed it needs marketing and distribution. This is especially true for games targeted to XBOX.

Anyhow, only time can show if time has comes for small teams and individuals to enter the commercial gaming market. Personally, I believe that a new strategic window is opening in the game development and this industry will see considerable change within 5 years from now.