You know whats great about questions based around an opinion? There is no wrong answer.
I picked Parliament and Sharp, because they're people who don't need to constantly remind themselves and everyone else that their good. Again, people won't agree, but I couldn't care any less, thats the whole idea of it being my list. Its important to remember in questions based around an opinion, that your OPINION of a person usually holds substance in your choices. This is one of those times..
I think you will find that there are several different people, with several different ideas of what makes a G.O.A.T. pvper. If there were a right or wrong answer, that would require us all to think like you. Its not hard to find the people on these lists who have done some previous campaigning on the topic. If you have a hard time remembering who has said what, all you would have to do is search their forum name. I don't think you would have to look back very far to get a direct or indirect example of what I am talking about. There are people out there who are great and don't care to be labeled. Those are generally the type of people I would want on MY list.
Michael Jordan never had to go from broadcasting station to broadcasting station, to remind everybody that he was the best of all time. There are just way too many people who I would qualify as a great player. If you really are the greatest, people just know it. I don't personally think this is a game where there is a greatest of all time, but its still fun to find who people believe they would be.
Robos name hasn't come up, I haven't seen Sigs name. I would venture to say those two could probably beat the majority of the 2v2 combinations listed so far. There will be tons of people who don't agree, but thats the whole idea of it being my list. Its just one of those things that are too close to call. It would be much more interesting to see a list on who are the best active PvPers. Even then, its just a list that would be based off opinion and personal experience.