In my experience, the second part of your sentence does not automatically follow from the first. It's not because a game is free that it will reach its maximum audience. For one because a lot of people ignore things that are free. For another because other people who can help you reach a much larger audience than you can even dream of, require that the game has a price (because they are commercial distributors, e.g.).
Initially I wanted the option to pay for advertising which only makes sense for commercial games. But since I don't feel that anything more than feedback posts or word-of-mouth will be necessary, I was starting to have some doubts... until I realized many gamers don't bother to wade through the 'sea of mediocrity' that is XBLIG or any site that has tons of user-created content, arbitrarily picking a quality threshold for their attention which starts as -- you said it, paid games.
Yes, iOS is an option except my game requires high poly characters (I will not be satisfied otherwise). I may attempt to release something with desktop specs but at iOS prices, but I don't want to set a trend of desktop price erosion -- it's already happening on the Mac App store.