If you intend on playing true 4-way games, and care about either truly going after score, or feeling like the original, then yes you need at least some way to have a true 4-way.
This can be through a switchable stick, a dedicated stick, or an optical/mappable stick like the U360.
8-way sticks will play 4-way games (obviously) but will frustrate you to no end if you are trying to play the game for any real length of time. The timing on those games is so precise, that one accidental diagonal up that results in you going left will be enough to anger you to the point of stopping play.
If you have no interest in trackball games, then you dont need a trackball. Its only other purpose is ease of use when using the computer without the front end, of course you could always just hook up a USB mouse when doing that.