I'm an hobbyist indie developer trying to go commercially indie.
What do you consider the most important in a game?
Atmosphere and exploration - depends on personal taste
Followed by world background and character plot
[Edit:] Ofcourse, this is after gameplay, as ApochPiQ mentions below. I'm assuming the 'game' part of the game is actually enjoyable.
What takes the most time during development of your games?
What could advance your games to the next level?
Good art and music and sound effects