McGinn has scored in each of Aberdeen's last seven matches and also scored against Portugal last month.
"Niall is an example of what regular first-team football does for a player," said O'Neill.
"He has the belief of his manager and he has repaid that trust by scoring goals - he's been excellent.
"He wasn't getting regular action at Celtic, nor on loan at Brentford, but now he's playing in a variety of positions along the front line and doing well."
Northern Ireland are still looking for their first win in qualifying, having drawn twice and lost once in their opening three games.