You can hit the link in pinside above for the TOP100 and notice that Monster Bash and Jurassic Park are both in the top 5.
You can look at details on those games online, but you should also probably try playing them, as others have suggested.
Perhaps price will be a motivator depending on what deals are available in your area.
You can also get some pricing info on this website for each machine that you can use as a guide.
You might want to take an experienced pinball guy with you to make sure that there are no big problems with the machine you select.
Since you are only getting one chance to get one machine, you will want to make an informed decision.

Just be aware that Alice Cooper's Nightmare Castle is a Spooky Pinball machine, not Stern, Williams, Data East, Bally or Gottlieb. That is not such a bad thing, but parts might be a little harder to come by or cost a little more. Most every pinball machine is going to require something to be maintained, repaired or fixed at some point. If you decide on that one, I would make sure that the manual is included, so you can identify parts that you might need at some point.