Silva is one bad dude. It's unfortunate that he was injured like this, but these fighters know the risks involved. I think Jon Jones has a shot at supplanting Silva as the most elite fighter of all time, but that will take many years to hold true.
GSP is fantastic and he had to step away. There has to be so much pressure to stay at the top, Anderson and GSP have both done a phenomenal job. As the champion, I would bet that each fight gets harder as you're getting everyone's best effort against you and you have to rise to that level and beyond each and every time. It has to be draining. I hope he recovers and does what makes him content. Weidman is the new sheriff in the middleweight divison after beating Silva twice.
For what it's worth, my favorite fighter is Sonnen, mostly because he is entertaining, yet he's also a physical competitor. Not elite, but good.