it all depends. I know thats the great answer to everything poker, but its true.

There are successful poker players with 20% pre flop and 40% preflop. Just more marginal situations to be played the higher up the chain you go. The bigger question to ask yourself is, Am I playing the majority of my hands in position, with the lead?

I personally play about 50-60% in 6 handed, until the table sees me as crazy, then drop down to around 30%. 10 handed, I'm in a full table right now at 40%, very passive table, and I'm doing fine on it.