What matters is... God's glory.

[A pious mind] embraces [God] no less as punisher of the wicked than as benefactor of the pious. For the pious mind realizes that the punishment of the impious and wicked and the reward of life eternal for the righteous equally pertain to God's glory. Besides, this mind restrains itself from sinning, not out of dread of punishment alone; but, because it loves and reveres God as Father, it worships and adores him as Lord. Even if there were no hell, it would still shudder at offending him alone.
  -- Calvin, Institutes I. ii.