Man, interesting thread, but way too many posts to read. I just gave up after reading like the first 10.
I honestly feel bad for this guy, since 4.5 years is certainly a long time. I guess the only thing I can say is that he should see it as a life lesson that had to be learned the hard way or no way. Sometimes that's just the way it goes. I haven't been through anything like that, and the longest relationship I had was a little over a year, and the girl and I were just incompatible, so the breakup was not as hard on me as it was for her, since she liked me more than I liked her for some reason.
Also, I agree with most people here that you need to just break off contact completely for about 6 months minimum, and you'll start getting over her, no doubt. It's hard to believe you will right now, but your mind is clouded by the whole breakup, so it's understandable. Good luck.
I'm glad to see that not all 4 year + relationships end in marriage, and if it wasn't meant to be, it's better to find out now than 10 years later after you have kids or something.