Yeah, it is tough to say, an a person's build has a lot to do with it. Like long arms can hinder the bench, but can help the deadlift, some guys with a bigger gut can use it to sort of push off when they squat and it helps them, also individual weak points come into play, and with respect to bench and squat if the equipment helps your weakpoint you get more, if not, you're out of luck. Like rbrown said, equipment isn't as much of a factor in deadlifting.
Personally, for an advanced trainee, I'd have to say it is acceptable for the squat to be about 50-100lbs more than the deadlift, and for the bench to be roughly 200lbs less than the squat. For me, my deadlift is by far my best lift, light years ahead of my squat, and I feel much more comfortable and natural deadlifting, but I was just speaking ideally.