1) Gottlieb - Usually have the best Rulesets for Single and Multiplayers, challenging, great artwork, unique features with their Roto and Vari Targets, and very fun especially for the experienced players. Of course every company had their dudes, but this company had the highest consistency of putting out great games IMO
2) Williams - Lots of Pointy People artwork, Ball Gates, pop up posts, unique features, and good fun in general for the whole family especially with their 70's Multiplayers and captivating the more experienced players with their 60's reversed Wedgeheads for a challenge with some titles comparable to the 60's Gottlieb Wedgeheads. Williams pointy people always put a smile on my face when I was a kid and screamed fun times ahead when I walked into an establishment that had pinball.
3) Bally - Zipper Flippers and mushroom bumpers were unique, pop up posts and ball gates, games usually interesting and fun to play especially with their 70's Multiplayer EM's, but they also had a few single players from both the 60's and 70's that could be entertaining as well. You could find pointy people artwork from this company as well, which is usually a hit or miss with pinball artwork critics.
4) Foreign pins -Sonic (Segasa)/Recel, etc - Of course I did not get to play a lot of these being a kid as they were not made for the USA market in general but you could find them here and there. They all had a uniqueness about their art/playfields/design, and rulesets that made them fun to play. From the few I have played, it seems that the Rulesets were as good as Williams machines, but not quite up to a Gottlieb standard. Generally they all played really fast because of the clear coated playfields and had good ball flow.
5) Chicago Coin (CDI) - Great Ball/Shuffle Bowlers and Gun Games, but there sure was not anything special about their pinball machines as the word "Lackluster" comes to mind both for single and Multiplayers with very few exceptions. It's almost as though this company designed pinball machines as an after thought, except for maybe the artwork. It seemed to me that their Multiplayers were actually far more interesting to play then their Single Players too, go figure.
Just my 2 cents,
Ken 
