Most Correlated option to ES?

What is the most Correlated option to ES with the highest liquidity/OI/Vol.?
Back in the very old days used to be OEX for example!
thanks

 

The most correlated options to ES are the options on ES. Otherwise, SPX, SPY and XSP.

 

...with the highest liquidity/OI/Vol.?

 

http://www.interactivebrokers.com/optionsCommentary/elitetrader/

 

Just look it up, bring up the chains and see which one is the most liquid.

 

SPY

 

Options on the SPX will have more OI and liquidity then you could ever need