Agree that Murray is better than all the guys you mentioned except Hewitt. 2xYear End Number 1, 2xGrand Slams and Masters Cup winner is pretty impressive (may have not been the strongest Era ever but all slams count) . I would say Andy and Lleyton are pretty even so far. Although Murrays likely to have the better Carrer by time he retires.
I'm talking about strictly who is better player. If Andy played in 2002, he would've been No1 easily. Andy Murray had more points as No3 then Lleyton as No1.