Most system 11 games revolve around the multiball sequence. Once you complete that sequence - repeat it. The fun is in seeing how many times you can repeat the sequence in a single game, which can very difficult on certain titles and very easy on others. A few of the later titles have some depth to them, such a Whirlwind with the cellar door value prize collecting, and Black Knight 2000 with the Ransom mode (which was basically the first "wizard mode" but is somewhat randomly awarded being that the RANSOM letters carry over from the game to game).
Then there are single ball system 11 games like Cyclone, Bad Cats, and Pool Sharks that have a lot of interesting gameplay rules that revolve around different playfield features, but there still isn't much "depth" to any of them.