Out of the games you listed, The Shadow is the best game. I have owned mine for 15 years and would be the last game I would sell. Johnny Mnemonic is your best choice for a fast playing game. Judge Dredd is good, but plays most like Road Show out of that group. Demolition Man is great too and plays different than anything else available. Congo is the perfect game for all skill levels with great design. Really not a bad choice on your list.

Demo man is a great game, underrated in my opinion , tons of flow. but im a huge roadshow aswell...

If you can get past the theme...I still think WPT has the most value\depth

Can you tell us how prices compare there? For instance how much is a nice Demo Man. How about Black Rose. Really I'm just trying to get an understanding of the price difference.

The big issue is that some of the crazy deep rule games are out of the price range. And in a collection of 1 or 2 games they will always get boring pretty quick. So that means you will be swapping them out more often no matter how great the game is.

Go with Judge Dredd. It's affordable, you've wanted it and it's the best theme out of the bunch. Other than it being a widebody, I found very little in common with Road Show personally. JD has flow and a ton of shots. Road Show had country music, stop and go and very linear.

The other pins you mentioned are excellent titles too. If you want depth and features, save up and get TZ. Great in a small collection.

+1 for Demo Man or WCS94, two of my favorite games ever, and two fairly cheap ones. Congo is no where near a bang for buck pin anymore, maybe a few years ago, but its price has definitely caught up with how good it is.

One recipe for a bargain pinball machine is great game play with an unpopular theme. One great example of this is Johnny Mnemonic. I struggle to think of another machine that can match the thrilling speed and flow of Johnny Mnemonic but the movie was a bomb at the box office. Someone has actually taken the effort to retheme it to The Matrix movies and it looks fantastic. It's easy to imagine that Johnny Mnemonic rethemed to The Matrix could fetch very high prices. Alas, it is a one-off and not for sale.

Another recipe for a bargain pinball machine is an acceptable theme, but with some flaw in the game play. Roadshow is a good example of this. The linear mode progression is something that can be irritating to some home environment players, as it has apparently irritated you.

The following list is a combination of both of the above and I think is a great starting point for bargain shopping. The prices are woefully out of date, but the sentiment is still true: http://gameroomblog.com/guides/the-top-ten-best-bargains-in-pinball-today

A summary of that list:
10 - Classic Sterns
9 - Johnny Mnemonic
8 - Demolition Man
7 - Jackbot
6 - Fish Tales
5 - Tales From the Crypt
4 - Judge Dredd
4 - Revenge From Mars
3 - Road Show
2 - Bram Stoker's Dracula
1 - Shadow

There's never a substitute for playing a game, but I found this Kindle book (from the same author of that blog) to be a useful reference, especially for pointing out game play flaws which are impossible to determine from casual play: http://www.amazon.com/Pinball-Book-Guide-Classic-Machines-ebook/dp/B009KZCR7U

The Matrix pinball:

Another excellent game to consider is "Indianapolis 500". Not easy to find, but if you do should be in the Shadow / Congo price range.