+1 to Potbelly's and Jimmy John's. Also to Chipotle's. Not a big Moe's fan. Their guac was terrible.
Subway is good when you're on the road and don't want to eat anything heavy. Quizno's is also tasty, but I prefer JJ's or Potbelly's.
However, my favorite subs come from a place in Michigan called Captain Nemo's. I think there are six of them, scattered throughout southeastern Michigan. Their sandwiches are divine.
If anybody reading this is around SE Michigan, look them up. Try their corned beef sub. I have never had juicier corned beef. Their turkey club is also fantastic, despite being loaded with fat and cholesterol. They also have breakfast subs.
Every time I go home to Michigan, I try to go at least twice. It's a 20-minute drive there, but so worth it.