Hard to compare due to technology advances over time.
I am getting into the simple but elegant rules on EM's and SS's. Take Gottlieb Volley and Lucky hand as examples in the EM category. The value of the drops changes with top inland's on Volley. The WOW calculations on Lucky Hand. As I play these games I just smile how a simple game to todays standards can be so much fun.
EM's are the best games to have friends over, bet a buck a game and drink beers. That does not happen with AIQ.
I am also leaning towards the Stern SS's as far as rules in the SS era ( Not counting EBD of course ). Stars is just a great game for scoring opportunities. Building up the bonus with the drops on Sea Witch is always fun as well.