There are vids out there of one guy (can't remember his name, I think he's Japanese though), got like 330k on the Castle stage, no cheating.
It is possible on the Gamecube one to use the AR (action replay) to do different things, there have been cheater vids of those people but Lorax and the Japanese guy I'm thinking of - they don't cheat for their scores.
He makes it look
soooooo easy too, that's what kills me.
I think my high is like 115k on the Village with Wesker and around 110k on the Village with Krauser. Those two boys...tons of fun right there, so powerful, lots of high priority moves, deal out tons of damage.