Teams have bad games. If City completely wipe the floor and piss all over PSG tonight then, yeah, I'd happily admit to being wrong, but I don't think that one draw (which they hardly scraped considering City led for a total of under five minutes), doesn't mean that City are as good as, or better than PSG. I mean, if we're going by that logic then I could easily point to PSG disposing of Chelsea last season, who were comfortably the best side in the league.
Looking at PSG's squad though, their dominance in the league, and generally decent CL form compared to any other English sides over the past couple of years, I'd struggle to argue that any PL side is better than them, or as good as them either. I'd certainly expect them to win the PL if you placed their squad into it right now, and I expect they'd comfortably be ahead of City.