top, middle, bottom tier

All the rankings on here are going to be a bit subjective... so here is an accurate representation based on tiers and not necessarily numerically ranking

Top Houses: these are the organizations you actually want to be a part of. All of them have strong numbers, strong social/campus presence, and for the most part good looking members
Fraternities - Sigs, Fiji, LXA
Sororities - Theta AGD

Middle Tier: these are your average frats/sororities. They have some average mixers/parties, decent looking members, and still better than being a GDI
Fraternities: Pike, Zeta Psi
Sororities:Alpha Phi

Bottom Tier: Might as well be a GDI at this level. The people who join these are either friends of people already in or didn't get a bid somewhere else. Have very few Hot members, mostly disorganized, and widely seen as bottom of the barrel in the greek scene
Fraternities: DU, Phi Delt, Any other frat trying to start up on western
Sororities: AOII, Pi Phi