fraternity tier system

Are you asking what the University uses as a tier system or the students? The university and IFC have a star system which is implemented through multiple things. None of which are the social existence on campus. Which is often times what the students use as a ranking system.

For the students, you're going to find controversial responses and a wide range of who they think is top house. But the most common you'll prolly find for the social aspect is:
1 Delts / Phi Tau
2 DU / AEPi
Snu / Lambda
3 Sig Chi / Pi Kapps
4 Theta Chi / Theta Xi / SAE
5 Fiji

Like I said though, lots of controversial answers as everyone's experience is different at each house. And this website shouldn't play a factor when you select a house when going through rush. Each house is different, go into it with an open mind.