Nice Thread

WH20 - The first pin I bought 8 years ago and still one of my favorites. Even those who don't play pinball love the flow and fun of the machine. It's easy to get a ways into the machine, but reaching Vacation Planner is quite another thing and completing it provides a real sense of accomplishment.
TZ - There are so many shots and things to do combined with a timeless theme. Lost in the Zone is achievable, but depending upon how you have your machine configured not trivial and not something you will not get every game that's for sure, unlike Final Frontier that was just a little too achievable.
MM - My neighbor has a MMr and I have to say it is just a lot of fun and a nice shooting game. There are so many things to do and ways to play the machine. Although I'm not a very good player as for me a 150-200 million point game is a really good game unlike Bowen that indicated that is an average game.
Shadow - Shadow is one of those games that constantly draws you back for just one more try at the final battle. It's fast, at times merciless, and really challenges your skills. There is a reason it appears in many tournaments.

The fifth game is tough. I have a Dialed In LE on order and I'm hoping that it will deserve a spot on the list based upon the reviews and feedback I've seen from those that have played it. In my case, until I get Dialed In, my fifth is a toss up between SM and CFTBL. SM has the flow between shots while CFTBL forces real control. With the JT spacing on the flippers and many of the tight shots close to the flippers the machine regularly humbles me. The two ball multiball sounds easy right up to the point of having to search and find the girl just to get the jackpot and then continue to make non-trivial shots to get the super. I always feel like I've accomplished something when I get a super on CFTBL.

Good luck with the list!