That really depends on what you liked about it. If it's proximity to politics and location, American and GW are similar. If you're looking at campus size or program, it can differ pretty drastically. You'll have to be more specific.
Definitely American and GW then. American has a more similar campus, but both of them have excellent International Relations programs. You can also look at Tufts, which has a really good IR program too. Georgetown's SFS is unique, but you can find pretty good substitutes.
@piuounnnnn I suppose you can classify me as one of those applicants who, on paper, "deserved to get in". I was waitlisted RD and eventually rejected, but let me tell you why I applied to UChicago in the first place. Unlike some other schools, I got the feeling fairly early that UChicago was a place where they really cared about the applicant beyond the grade. I know most schools are holistic, but UChicago seemed like they REALLY cared about an applicant's other aspects. So the only thing I can conclude from this is that if they took you, something about your application must have stood out to them. Adcoms don't make very many mistakes. If they accepted you, it means they thought you had something they were looking for, even if your grades were below their average.