Yep, always an interesting question to ask !!!
My top ten games are:

1- Blaster
2- Stargate
3- Robotron
4- Tempest
5- Gravitar
6- Major Havoc
7- I'Robot
8- Space Duel
9- Sinistar
10-Turkey Shoot

Major Havoc and Space Duel are the only games missing in my gameroom, but they are the next that i want to buy. For a deep collector like me, i don't have choice to buy on ebay, otherwise it is impossible to get those games. If you know someone around Montreal who sell his Space Duel or Major Havoc, i offer 1000CAD$ ( more for a MH dedicated) for one in good condition without question !!! I can get a Space Duel easily on ebay, maybe the next one i will buy very soon.  

Mine are:

1- Battlezone
2- Missile Command
3- Tron/Discs of Tron
4- Centipede
5- Robotron
6- Satan's Hollow
7- Defender
8- Tempest
9- Asteroids
10- Moon Patrol

I have three of the machines on my list, the Battlezone, Tron and Centipede. Currently looking for a Missile Command (especially the cockpit version), and might be getting a Satan's Hollow soon  

BattlezoneMan

You have very big dream like me !!
Missile command cockpit and Major Havoc dedicated ( for me) are almost impossible to find these days ! In 1984 my friend bought a Major Havoc dedicated for 500cad$ from the local operator .....ishhhh. Someone on the net ask me 4500us$ for it this week. I wish you good luck

One day I hope to have them all. I know that the Missile Command cockpit is extremly rare, but I can always dream  

Also looking for a Discs of Tron, Environment Version. Those are getting harder and harder to find these days too. I knew someone in my area who had one a few years ago, he thought is was worthless and almost threw it in the garbage (complete and working). He ended up selling it on the net to someone for $500.  

I wish you good luck too. I'll ask around for you for the Major Havoc, I might know someone who has one for sale at a reasonable price

BattlezoneMan

My List:
1- Galaga
2 -Pacman
3 -Joust
4 -Centipede
5 -Asteroids
6 -Tron
7 -Stargate
8- Reactor
9 -Tempest
10 -Dragon's Lair
I have 1 to 7 on my list, but the last three are tough, Maybe someday.

If you have big money, there's a lot of Tempest on ebay !

My top 10 favs:
1) Mario Bros.
2) Gorf
3) Asteroids Deluxe
4) Tron/Discs of Tron (has to be enviro)
5) Star Wars (has to be cockpit)
6) Paperboy
7) Track and Field (the BEST 4-player game)
Monaco GP
9) Frontline
10) Twin Cobra

Honorable mention:
Moon Patrol, Space Duel, Sinistar, Defender/Stargate, Star Castle, Galaga, Robotron, Burgertime, Championship Baseball, Street Fighter II (any edition), Armor Attack, Donkey Kong/DK JR., Super Pacman, Mappy, Food Fight, Elevator Action, Sprint 2, Karate Champ, Yier Kung Fu and Bagman

Front Line...wow... not many people know of that one... played it a lot as a kid... I know where I can get one for about 100$...dedicated, but not completely working...Same place has a Monaco GP (not Super Monaco GP)for next to nothing...

Since I'm limited on what I can have, I have to pass on them...

Got the Frontline already and love it. I used to the play the hell out of it back in the day.
As for Monaco, there's a local operator that has a ton of them sitting around, it's just a matter of time before I wind up with one. I always loved that game. Maybe it's because when I was a kid it was one of the few games that I was tall enough to actually see the screen on.