Dante. As much as I love Vergil, Dante's always came first over him. I also prefer his personality because it's fun and he likes to party. You'd think that by all of his cheesy lines in the games ("I SHOULD HAVE BEEN THE ONE TO FILL YOUR DARK SOUL WITH LIIIIIIIIIIIIIIIIIGHT!" anybody? and, "My soul is telling me it wants to STOP YOU!" fagga) that he'd be a very cheesy character with no depth, but this is not so. His character gradually grows over the course of the games, but he'll always have that personality we all love (as we see in DMC4) and that's what's important. Plus, he's totally stylish and cocky! I love all of his outfits in the games. My favorite definetely being Dante from DMC3 at the end of the game in his DMC1 attire.
And all that said, it doesn't mean that Vergil's any less of a great character. He's awesome too! I just love Dante more... I have a thing with liking the main characters (especially the good guys) the most.