The answers to your questions are short essays in them selves!
Games can be written in almost any language, for almost any platform, as has been proven time and again, when nerds port Tetris to Casio calculators, and Doom to dishwashers.
It really depends what sort of game you want to create: are you thinking that you want to create the next Halo / Crysis or is Line Rider / Armadillo Run more the kind of thing you are interested in?
The former take teams of a hundred people working at the cutting edge of technology for many years, while the latter will run on decade old machines, and could be written by an individual or small group of friends. The playing-field really is that open!