There are many "Top 100" lists on the web that rank pinball machines.  They do vary, but are very helpful in helping you select the perfect machine for your gameroom. 

Here are links to a couple of these rankings:

Pinside - "Pinball Top 100"

http://www.pinside.com/opinion.top100.asp

Arkadia Amusement Games - "e;World Pinball Top 100"e;

http://www.arkadia.nl/pinball/diverse/index031_top100.htm