Question: IPDB says Street Fighter II has a 3-level playfield. What do you guys classify it as and why?

The lower playfield would be the "Car Crusher" - there is a ball and flipper under the main PF.

Then there is the standard PF

The top mini PF is small, but it also has a spinning flipper

Technically - it has three levels

A "level" would be difined as a part of the game which interacts with the game - ie - thumper / bumper / flipper..