Well legally if someone is super drunk they can't give consent = having sex with them is rape (legally) I will admit that lots of people both get drunk and to me this is not rape, however if legally someone can't give consent, like when they are drunk, you have to make sure and be extremely confident that the person wants to have sex with you. I wouldn't be satisfied with anything less then 'Do you want to have sex?" "Enthusiastic response such as Yes!!!! let's go!!"
It is NOT cool to stick it in someone and wait for them to stop you. You have to give them the choice before you make a move, because stopping someone from doing something can be harder and intimidating.
I admit there is grey areas in the sense that you may not know whether it was rape, but there is not a grey area as to whether it was rape or not. This is where you are putting yourself and others in danger, by not being sure if what you are doing is wanted.
At the end of the day it doesn't really matter what the general population would say, it matters what the person it happened to thinks about it, whether they consented and wanted it to happen.