It's a tough choice for me. Hulk Hogan in his prime was always great to watch, but of those listed, the only ones that I feel could still go in the ring* are John Morrison and Batista. I never saw any of Batista's work post-Evolution, but I wasn't a fan of his Evolution work. Thus, I voted for John Morrison. I was a big JoMo fan when I returned to watching, but by then he was on a jobbing spree and decided to take time off.
Every superstar adds something, so I'm sad when any of them go, but the ones that are the most sorely missed are the ones that still have good matches left in them.
*I have not watched much TNA, so I can't speak for the current talent of the listed former WWE stars that are now employed there.
I wouldnt usually say this and would choose someone else but Batista.
Not the greatest guy in the world but just a few years ago Smackdown was a legitimate programme that rivaled Raw in my opinion with Punk, Batista, Edge, undertaker JBL, Jericho, hardy.
WWE needs somebody like him back to bring back some prestige to Smackdown and enhance the card, im also a big fan of if your good enough your big enough but and size is irelevant, but WWE really could do with more legitimate top drawer big guys to add a dynamic to the current smaller roster.