The giant striker's hat-trick against Newcastle took his tally to nine in an injury-hit season.
"To see him up to nine goals now is great. There's no reason why he shouldn't be a 20-goals a season man, O'Neill told the Birmingham Mail.
"That's the sort of thing I'm looking for from him and Gabby Agbonlahor, with Marlon Harewood playing a part at this minute because we're not getting enough goals from midfield from open play at the moment and yet we're the third or fourth leading scorers.
"The very fact we are talking about him means he might be getting a wee bit more consistent.
"I'm not asking him to score a hat-trick on a consistent basis - although it would be fantastic if he did - I want him to up that consistency a notch more.
"Even when he himself has felt he hasn't played well, that hasn't been my view of him.
"I think he's a miles better player than he thinks he is.
"When he has that sort of strength and determination about him, he does wonders for us.
"He's a nightmare for defenders, but not just with pace, power and presence - he has great ability to get it down, manoeuvre and being people into the game.
"Maybe he could be a bit more selfish at times, but he has that capability."
O'Neill continued: "I was delighted he scored the hat-trick and he has that ability and it's up to us to try to get it out of him on a more consistent basis.
"I think he can do it, without question. When he's in that sort of mood, not only is he a fantastic player but the crowd are right behind him and they love him.
"He's a player whose game is based on confidence - most players are - but some more so than others.
"Since he arrived at the football club in the swop with Milan Baros I've been delighted with him.