Rick is definitely taking on the roll of Shane as you stated. With season six just beginning, we're now seeing a darker side of Rick Grimes that is not being told. What is this side? Continue to read and I'll explain. In season four Rick began showing signs of the Governor. What were these signs?
1) Rick bites into the neck of Joe. The Governor bites off Merle's fingers.
2) When Rick's in the chruch he cuts off Gareth's head using a machete. Rick does this when Gareth says, "If you let us go, you'll never see us again and we'll never cross paths again" This is as opposed to when Rick is at the prison. The battle for the prison. Rick looks at the Governor and says, "It doesn't have to be this way. We can survive and live together. We, you, can come back from this. We have to." That's when the Governor looks at Rick, says "Liar" and cuts off Hershel's neck with Michonne's sword.
3) Finally we come to Alexandra. A town of civilized life with just one problem, Rick's not leading the town. Why does this seem familiar I wonder? A man that in season six starts running the town and is trigger happy.
In closing, were seeing untold story unravel, Rick's becoming the Governor and Shane. So, what fate lies for our fierce leader?