Grievous/Kun/Malgus vs. Katarn/ROTJ Luke/Kenobi

Battle takes place on neutral ground

Grievous gets stomped quickly, so it's mostly 3 on 2. Still...Kun is nothing to sneeze at, and he's already beaten a stronger version of Luke. Hmm...

Team 1. Grievous wouldn't be getting stomped by anyone on the other team, and Malgus and Kun's combined power (should the latter decide to actually use it) would be far too overwhelming in the long run.

Luke or Katarn lack the showings in the force to suggest they'd destroy Grievous with the force IMO

Indeed.