Let's see: top 30? (and no peeking here):
Ruth
Mantle
Reggie Jackson
Gehrig
Dimaggio (?) - hmm not sure anymore if he is still in the top 30.
Then, thinking of players that made short appearances as Yankees or who were not only with the Yankees:
Not sure about Cecil Fielder, Daryl Strawberry, David Justice (don't think so). Is Dave Winfield on the list? I don't think so but he could be.
I am going to guess four, the top four on the list above. I am pretty sure I am not right.