Mourinho, who left his role as United manager last season, also ruled out any hope of his former club Chelsea toppling City as champions.
Asked who had the resources to challenge for the title this season, Mourinho told Sky Sports: “Man City, Tottenham, Liverpool and Man City B team.
When I looked at the bench [against West Ham], the players not involved, I think the [City] B team could fight for the title.”
Mourinho, who was working as a pundit for United’s 4-0 thrashing of Chelsea at Old Trafford , added: “We would love United, Chelsea and Arsenal to also be at that level, it would be something incredible.
“But we are speaking about a team that won everything in England, we are speaking about the European champion and the European runner-up.
Then we are talking about United sixth, and playing Europa League and Arsenal fifth and Europa League too.”
Mourinho said that a realistic ambition for United this campaign would be to emulate his achievement with them of winning Europe’s second-tier club competition. “As a start you need to win the Europa League,” he said. “When you go to a competition like that, you have to win. If they finish in the top four [in the league], it is a good season.”
He was optimistic about his former player Frank Lampard’s hopes of succeeding as Chelsea manager, despite defeat in his first competitive game in charge.
“What Frank was as a player – does this give him a capital of trust, especially in a relationship with the fans?” Mourinho said. “Yes, it does. By having Frank in place now, they didn’t buy players, but they bought time. I think he will get the time that other managers may not have.”
On the other title contenders, Mourinho said: “I don’t see also Arsenal to [last] a title race, but I think Tottenham has to join it.”
Fellow Sky pundit Gary Neville agreed regarding his former club United, blaming frequent changes of philosophy for their problems. “I don’t see United winning the title,” he said. “As a United fan all, I want them to do is to create a strategy and stick to it.
“They sacked David Moyes, then LVG [Louis van Gaal] came in, a lot of technical possession players to fit his model. Then they sacked him.
“Jose came in, signed [Eric] Bailly, [Zlatan] Ibrahimovic – very physical – gave him a new contract, then cut that path short. Then [Ole Gunnar] Solskjaer has come in with British players. Four different strategies. Don’t keep changing all the time. ”