the 5 fat gram sandwich you think you're eating is really about 14 or so after adding cheese, mayo, oil etc.
Mayo? Oil? Ick! Easily fixed... get honey mustard instead. Much tastier than mayonnaise or oil, and very little fat. You need to add a few grams of fat for the cheese, of course, but the result is much less "fatty" than most fast food.
As far as Arby's is concerned, I do like the Market Fresh sandwiches. However, as
vi_edit mentioned, they're not nearly as healthy as Arby's would have you believe. They do have a "Light Menu" with a few sandwiches that are much healthier, unfortunately those sandwiches also have only 230-250 calories -- hardly enough for a full meal. And since they don't really offer anything else semi-healthy to go with them... you need to avoid being tempted to order french fries or something
unhealthy to accompany them!
So, I agree with the previous comments that Subway is really the only widespread fast food chain that has reasonably healthy food. You do need to be careful with other sub chains, though, since not all are as healthy as Subway. Jimmy Johns, for example... if you check the nutition facts on their website you'll find that most of their sandwiches are quite high in fat.