The real "rankings"

You can't truly rank the sororities. Too many factors and too many subjective opinions. But, you can draw some pretty broad lines around groups.

Traditional Top 6. They have been "top tier" forever, and because of that history it isn't likely to change. Sure, suspensions can knock one down for a bit, but money and tradition bring them back:
DG, PiPhi, APhi, Theta, KD, KKG

Traditional Mids. These houses have been around forever in one form or another. They all have taken turns at the top of the mids and at the bottom, and it will all get flipped again some day as things occur. Each of these houses have strong history at OSU and all have something going for them:
TriDelt, ChiO, AGD, AoPi, Fuzzy, DZ, ZTA, AchiO, AePhi

Gamma will be right there with the rest of the mids. They are "newer" on campus but are doing great and while not traditional here, they are a strong house.

The point being, stop trying to rank these houses. Best you can do is throw them into these general buckets. If you want to be uptight and say nothing matters beyond the top tier, go for it. But that doesn't change the fact that each of those mid houses have a bunch of high quality girls and great sisterhood, and a lot of support from alums. No one should think twice about joining any of these houses.