My pick would go to The Shadow, due to balanced scoring and interesting rule set. Attack from Mars would be a close second. MM is great too, but the castle tends to attract too much focus during gameplay.

Supposedly the empty space was originally intended to allow the UFO to navigate around the playfield as a moving target during the attack wave.

According to Brian Eddy:

"AFM was the most different. It had one big feature that didn't make it into the game. The saucer in the middle of the playfield was originally suppose to move out and around the playfield.
It started (rested) right where the static one on the final game is. It had a telescopic arm that allow the
saucer to move out about 18 inches onto the playfield and a pivot that would rotate it right & left.
So it basically could "move" around the whole playfield (hence the open playfield area in the final design).
It also had a target hanging down from the middle of the saucer that you could shoot from
any angle. We ran out of time to develop it and keep it cost effective.
It was also a reliability issue and to make it rock solid would have required a lot of testing time."

Here is where

Here is where I learned about the original AFM design.

http://hem.bredband.net/b257182/eddyinterview.html

To me, The Shadow is not based on the movie, but is a beautiful Art Deco style pin based on the classic old time radio show and pulps... I just need an alternate translite to fully realize this. *cough, Aurich, cough*

Is he currently working on another pin?

Well if Pat Lawlor is designing game number 3, this seems entirely possible. Very exciting! Has the theme for 3 been announced?

I see, what is the alleged theme? Is it a license or a completely new IP?

If he's not currently working on one, he should be! I think it would be very well received. Did he ever say why he completely migrated away from pin development? I understand that Williams was on the decline, it wasn't a growth industry, and digital entertainment was the future. But was it he no longer enjoyed it, or just wasn't viable?

I think each are winners in their own way. Here is the breakdown in my opinion:

Rules
1. AFM (So much to do here, rules encourage many different types of gameplay requirements preventing the central toy from dominating)
2. Shadow (Offers mode based scoring that offers much more to do, again lots outside of wizard mode requirements)
3. MM (Troll, extra ball, Merlin overlap complexity, castle seems to dominate a bit more)

Flow
1. Shadow (Diverters, extra flipper loop, clean orbits - AFM and MM will block the loop as part of the game).
2. AFM
3. MM

Wizard Mode
1. MM (Full on battle that is very difficult)
2. Shadow (Possible to win or lose on skill)
3. AFM: (Very difficult to lose, and fixed score amount: $5B)

Scoring Balance
1. Shadow (Very balanced scoring)
2. AFM (Many things to do here and ways to accrue points)
3. MM (The castle seems to dominate the focus)

Playfield Artwork
1. AFM (Stylish 1950s alien attack, just works with pinball)
2. Shadow (Design style with gold ramps properly embraces the art deco style of the period)
3. MM

Toys
1. Shadow (Diverters, magnet lock, battlefield)
2. MM (Very cool central toy)
3. AFM

Looks like it’s down to AFM for Shadow for me!

Is Shadow or AFM being remade this year? I agree, higher cost doesn't mean more quality. Part of MM's appeal was its easy to get rules that led to mass appeal. I'm sticking with my vote of Shadow on this one. Shadow has the most diverse gameplay and the longest replayability of the 3 listed. That alone makes it the winner.

Or worse case scenario, do a complete reskin, ala Family Guy/Shrek! Base it off the radio show.

Although Aurich has pretty much already allowed us to realize this with his awesome alt translite.

Haha

Don't know if that counts!

The poll should be updated to include Stranger Things.