I am thinking of going to gencon in 2017, and am starting to consider hotels. However, for cost reasons, a downtown hotel isn't in the cards for me. Can anyone give any recommendations for good hotels outside the downtown area? I have heard that the southport and airport areas are popular, can anyone name any specific places?

First question: how do you intend to get downtown each day?  Rental car?  Uber?  Buses?  Each one has different answers.  (For example, very few bus lines serve the airport hotels, but you don't have to worry about finding a place to park each day.)
 

If you are driving to GC and will be driving to the convention each day, I would not just limit my search to the airport or southport areas you mentioned. I believe there are close to 20+ hotel in the area surrounding the city off of the major roadways (70, 65, etc...). I use points from my cc to stay at one of the many hotels that are a part of the Wyndam Hotel family; I actually already have my room reserved.  I would take a look at their website as they have many options that should fit your budget that are maybe 12-15 minutes (they have closer too) from the convention center.

Parking in the city can be an adventure and costly if you do not get to the city early enough so that you can have your pick of locations. Gate Ten had an amazing deal this past year on spots in their location that probably saved me $30-$40 over the 5 day span. I would highly recommend grabbing one of those tickets when they become available during event registration (if Gate Ten offers it again that is).

If you are driving, I hope this helped!