The best way to know is to play them.
To me, there are two things that make or break a pin.
1) Things to do.
Many of the older games do not have enough to do, so you may
boar of it very quickly. This can sometimes be negated by #2.
2) Ball Flow
A game with poor flow, will often mean that the ball will slow down,
losing its momentum often. This makes the game slower paced,
less challenging & much less fun.
A game with great ball flow will allow the ball to move from one shot
to the next in a series of combination very quickly. The ball can end up
a blur as it travels mach 5 all over the field, every flip making it even
faster.
Some people Prefer the Stop-n-Shoot games, where I prefer smooth
ball flow games. Still, from what Ive seen... the stop-n-shoot guys
can still like smooth flow games... where as its rare that good-flow people
like stop-n-go machines.
Best bet is to give any game you intend to purchase a few games
and see for yourself.
Virtual Pinball machines may give a slight indication.. but do not let that
be the reason. Games played for real, usually play much much different
than the virtual tables. The physics just are not good enough yet.