Really good thread and interesting topic.
For a smaller collection, up to 5 or 8 pins, the most important question will be how to balance or include/exclude a common theme with the importance of variety. Even though I like horror themed pins I could not imagine putting Freddy Krueger+ BSD+ MSF+Scared Stiff+ Haunted House in a home lineup - even if it would look awesome on display. It would feel to onesided.
I could imagine the following games in a perfect five machine line-up
If a sixth game could be added -it would be a EM-player. Most likely one of Gottliebs Wedgeheads. I would probably stick with my current title Ice Revue- which looks great. My wishlist for alternatives would include Card Whiz or Target Pool.
An awesome mix, with depth enough to make it interesting.