For SS I too vote for  Firepower . It is fast, unforgiving and forever challenging to play .
Low scores and blindingly fast games are quite normal which keeps you wanting to come back and try to beat it .

Good to see there is some love for Black Hole as I recently bought a project one (currently in pieces), and looking forward to getting it up and running .

I don't have a particular EM to recommend but strongly suggest getting a single player game because any bonus etc carries over from ball to ball which , to me, makes the game more enjoyable .
Also, I've found many Williams single player EM's are just as good as Gottlieb's and are usually much cheaper .
One example is Gulfstream .