A bit south of "south loop" is Manny's Coffee Shop and Deli at 1141 S. Jefferson. (1-312-939-2355). It's a New York style deli with huge portions of kosher style, but not kosher, food. My favorites there are the corned beef or the pastrami sandwiches, the potato pancakes and the cheese blintzes. The parking lot is often crowded at lunch time, but usually there will be some street parking available. Manny's serves breakfast and lunch and closes at 4 PM and is closed on Sunday.
Opera and Gioco are great (near the intersection of 13th and Wabash). However, as a resident of the neighborhood, I agree that free parking is something of the past. Friends don't want to drive to visit anymore because street parking has become nonexistent in the past year. Still, both restaurants offer $10 valet.
Not exactly the South Loop, but there's good soul food to be had at:
3901 S. Michigan Ave.
Usually plenty of parking on the lot just north of Pearl's on 39th st.
I've also been able to find parking weekdays/early evening on Wabash across from cuatro. Whether that's available for lunch, you'd have to check it out. Otherwise, as I'm sure you know, street parking in the South Loop is somewhere between a hassle and nonexistent.
2030 S. Wabash Ave.