Alexandra Burke, Eoghan Quigg and boyband JLS will all compete for the £1 million recording contract following the elimination of Diana Vickers last night.
Speaking on The Xtra Factor, Cowell insisted that he is currently clueless about who will be triumphant on the night.
"You know what, I think this is, without question, the most open final we're ever going to have," he explained. "Any one of these three could win it now.
"No one's going into this final as an underdog and I wouldn't like to put my money on any of them right now. It's all going to be down to performances [and] song choices on the night."
Cowell also confirmed that he has special guests lined up to duet with each act, but refused to reveal their identities.
The X Factor final airs from 7.10pm on ITV1 next Saturday.