Moyes has yet to guide West Ham to victory since his arrival at the club on November 7, with the Hammers losing at Watford and Everton either side of a 1-1 draw at home to Leicester City.
Meanwhile, Pep Guardiola's Premier League leaders have not dropped points since their 1-1 draw with the Toffees back in August, and victory over West Ham on Sunday would see them equal
the record of 13 successive Premier League wins in a single season set by Chelsea and Arsenal.
Despite City's dominance, Moyes told Sky Sports that Guardiola's men still have to prove themselves before they could be called a great team.
"I wouldn't say they've got a long way to go but what I would say is they've not done anything yet as far as they've not won the [league] yet," said Moyes.
"And I think there's been some great teams in the Premier League who have won it over the years. Maybe at the end people will say they are a great team but until that's done then you can't really say so.The former Manchester United boss travels to the Etihad Stadium hoping his side can avoid defeat and save him from an unwanted personal record.
"I don't think they're completely unflappable with what they've got."
Moyes has lost his last four in a row against City and if West Ham lose on Sunday Guardiola's men will be the only club to record five straight victories over the Scotsman.
Despite his record Moyes was in confident mood ahead of the trip, saying: "I think there are ways to play against them, I think they've got weaknesses.
"They play very high up the pitch, which can leave space in behind them.
"But I think the coach [Guardiola] admits to his frailties and knows what the weaknesses are but tries to make it so difficult for the opposition to get to their weaknesses."