I've only been there once since they've moved to their new(er) location, but I've always enjoyed Pat's Pizza. I also second the recommendation of Marie's, not only for its pizza, but for its genuinely retro atmosphere.
Pat's Pizza
2679 N Lincoln Avenue
Chicago, IL 60614
In the South Loop, there's an (unrelated) Pat's Pizza in Printer's Row, which I think serves up some very serviceable thin crust, especially for the South Loop. That was my go-to place for pizza in the loop. It doesn't really have much of a dine-in space, but it's nearby.
Pat's Pizza
628 S Clark St
Chicago, IL 60605
Personally, I think if you're here visiting with your gal, Marie's is your best bet.
(Also, you wouldn't really be taking the red line to get to Vito & Nick's. Orange Line to Pulaski, transfer over to the 53A Pulaski bus south.)