Who is the best fighter in UFC 6?

There is not one. There is a best fighter for pressure, for counters, for wrestling, and for subs — and only if that is how you play.

Are 5-star fighters always better?

They have more tools. They still lose if you fight against their perks or you cannot deny a shot.

Yes, with patches. Distance and takedown defense do not.

The 'best' fighter is the one whose perks match what you already do in a round. Someone else's top 5 will not play your game.

Best UFC 6 fighters by playstyle: pressure, counters, wrestling, and submissions — pick the card that matches your hands.