First, I know it is probably sacreligious to be asking for phili cheesesteak outside of philly, although it's not as easy to get back there everytime I have a craving. I'm currently in Indianapolis looking for the best possible cheesesteak.
Having lived in both cities, I can say with some certainty that you cannot get a real cheesesteak in Indianapolis. Lots of places try (and some even make pretty tasty sandwiches), but it's not really authentic.
Steak Escape in the City Market downtown does an acceptable job in a pinch. You can't get it Cheez Whiz though, and you probably won't belch grease for hours afterward either. All in all, not very close to the authentic Philadelphia experience.