It is much more common among mac games to have a windowed option than among PC games. However it is not required. The type of game and style of game play, I feel, are more important to offering a windowed option than the platform. Such as a casual non-timed puzzle game where if you get a phone call and have to look something up in another program, that's a perfect candidate for a windowed mode of play. However for something very involved, that's more of an experiance to play, such as a FPS or racing game should always be full screen as, if you can't focus on it, you can't play it properly. Also if the game takes over the mouse it should always be full screen as if the mouse leaves the window and someone clicks on the desktop by accident rather than shooting that badguy on the far right of the window it ruins the experiance.
As far as having windowed mode as the default that depends again on intended play style. If you intend for people to sit down and play the game for a good stretch without doing anything else then you don't want the distraction of the menu bar, blinking chat programs etc. However if it's a quick pickup and play for 5 minutes while you wait for someone to call you back type game then you want them to be able to get out quickly, like mine sweeper.
One last note, if the game does have a windowed mode of play, regardless of if it is the default or not, it should always remember if it was windowed or full screen when it starts and revert to the last used setting. If someone likes it full screen they REALLY don't want to have to switch in EVERY time they play, and the reverse is true for windowed mode.
Hope that helps!
As far as having windowed mode as the default that depends again on intended play style. If you intend for people to sit down and play the game for a good stretch without doing anything else then you don't want the distraction of the menu bar, blinking chat programs etc. However if it's a quick pickup and play for 5 minutes while you wait for someone to call you back type game then you want them to be able to get out quickly, like mine sweeper.
One last note, if the game does have a windowed mode of play, regardless of if it is the default or not, it should always remember if it was windowed or full screen when it starts and revert to the last used setting. If someone likes it full screen they REALLY don't want to have to switch in EVERY time they play, and the reverse is true for windowed mode.
Hope that helps!