Are there less than 1000 P3 systems out there? I would guess so. There are probably less than 1000 Bride of Pinbot 2.0s too.
JJP PotC 1000 units
Caribbean Cruise 337 units (cocktail pin)
The Big Lebowski
Cactus Canyon 903 units (for now)
Rob Zombie is fun.
Transporter the Rescue is certainly striking. 859 units
Godzilla Sega. Only 510 units (!).
I've played Kingpin and Big Bang Bar. Not enough to really form an opinion though.
Other candidates not yet mentioned:
Punchy the Clown (I have a soft spot for this game)
NBA Stern (I'm sure this game has its fans)
Full Throttle (probably less than 1000)
Lost in Space 600 units
Super Mario Bros Mushroom World