Quoted from 1974DeltaQueen:I'm with jr : Pleasure Isle
1b. Diamond Jack
1c. Cowpoke
The tough part of the question is that EMs spanned many years. Completely different from one era to another and each one has it's own unique characteristics.
But if I had to pick one machine....then I'd agree with JR and Delta that Pleasure Isle has many of the great classic features that keeps bringing you back for another game. It's one of my favorites and a keeper. I'd choose this one for the 60's EM metal rails
El Dorado for the 70's
World Champ for the 50's woodrails
Barnacle Bill for the 40's
Major League for the 30's
My $0.02