OP, since you are a newbie, I'll cut you some slack. Your question comes up on a regular basis. What you need to realize is that the Pinside Top 100 is a crowd sourced accumulation of rated games, that is stack ranked based on those ratings. The ratings are from all kinds of people, with all kinds of pinball experience, and both owners and non-owners of the games rank them.
IMO, the list is useful when you don't know much about pinball titles and need somewhere to start to see what's popular. From here, based on your interests you can pick a few games and start researching them (e.g. going to a game specific thread and reading the posts) and hunting them out in the wild to play (e.g. arcades, pinball events, etc.)
The list typically features new releases at the top, but there are also some great classics with staying power. If you like a game that's not high on the list, who gives a rip? If you like it then stop worrying about what others think. Conversely, if you only prefer games that are highly ranked, then you will find that others don't give a rip. Ultimately, the Top 100 is just a fun way to present popularity and likability of games in general.