Greater blink is also rather nice as a melee buff for an eldritch knight style character. Ghostform gives you a 50% miss chance with all your attacks unless you have a ghost touch weapon (which, even if you do have one, is not the most efficient enhancement to have on your primary weapon). Greater blink doesn't give you a miss chance and also lets you strike as invisible (except that blindfight does not help). It's probably not a big deal, but ghostform also negates any natural armor bonus you have and greater blink does not.

I would think that all told, greater blink is a clear winner if you want to attack your foes with weapons and ghostform has an edge for someone who just wants to contribute with spells.