Tie between 3 & 4.
And no, I do not think 4 is as good as 3. So how are they tied? 3 is awesome, and has Vergil. It has great unlockables and the script is tons better.
I also chose 4, because I'm a sick f*ck, pure and simple. DMC4 is like one giant masturbatory aid. It's pretty, Dante makes me want to pull him out of the screen and rape him. Dante/Nero anyone? Hello? Nero obviously wants to ride the albino cowboy. OH, AND THE LUCIFER SCENE, AND TRISH AND LADY'S ASSETS.
DANTE'S COWBOY BOOTS.
There. I said it.