Spurs inflicted Real's biggest Champions League group-stage defeat in nine years as they ran out 3-1 winners, whilst City beat Serie A leaders Napoli 4-2 in a pulsating encounter.
Speaking on 'The Debate', Bellamy said that despite Spurs' win being impressive, City deserve more credit due to Napoli's recent form, with the Italians yet to lose in the Italian top flight after winning 10 and drawing one of their first 11 games of the new season.
"It sounds crazy because it's Real Madrid and they haven't lost a group game in five years, but I felt if Man City could go to Naples and win that was a big win," he explained.
"For me, that was Manchester City's biggest challenge of the season. Of course they've had Chelsea, but look at the form Napoli are in at this present moment.
"Real Madrid are not in great form, but the way Napoli have been playing at this moment, for Man City to go there and win is incredible.
"Napoli are one of the form teams in Europe, a possession-based team.
"I've been really impressed with Napoli. Playing-wise in European football they have really impressed me this year, so that is a really good win.
"That's a really good statement for Pep Guardiola's team."
That's not to say Bellamy wasn't impressed by Spurs though and the former Liverpool forward believes that results of this ilk may become more commonplace in the years to come.
"For Tottenham and where they are looking to go in the next few years, they needed this," said Bellamy.
"But I don't see this being a one-off.
"I see Tottenham under Pochettino being here for a while and getting more results like this in the next few years.
"They are here for a long time."