Although Real Madrid are safely at the top of the La Liga table but still, Real Madrid do not have really impressive results in the Champions League matches this season. Moreover, Real Madrid will have to face Manchester City although indeed, Manchester City also sometimes fails to get a win in big matches as happened lately also in the Premier League against Arsenal which ended in a goalless draw. Therefore, any result is still very likely to happen in the match between Real Madrid v Manchester City in the quarter-finals this time but even so, I think Manchester City still has a slightly higher chance than Real Madrid at this moment.
Actually I disagree if you say this season in the Champions League Madrid has not provided an interesting thing because seeing from what happened throughout Madrid's journey in the Champions League we can see their statistics are very good starting from the group phase to the round of 16 some time ago where 7 wins and 1 draw they managed to get during the Champions League and these statistics are not much different from what Manchester City did in their matches in the Champions League.
When saying they struggled against Leipzig I don't think that can be used as a strong reason because however Leipzig is indeed an opponent that is not easy even in the group phase Mancehester City was also quite troubled against Leipzig and we cannot eliminate that fact.
I think the stigma of Madrid being considered weaker than Manchester City needs to be changed because after all, it is precisely with that that Madrid has a good opportunity to plan so that the results this season are different from what they got in the previous season.