Having been there a few times, I find Paris rather cold…
Aside from the big landmarks : Notre-Dame, the major museums, the famous monuments... everything around them feels pretty grey and dull overall.
Maybe I just went at the wrong time, but honestly, there's nothing extraordinary about it.
In general, most big European capitals are quite disappointing.
Brussels, though... aside from a few really rough areas and some no-go zones, actually has some very nice spots.
It's just a shame that mass immigration is destroying so much of it.
Bruges and Ghent, and Flemish towns in general, are beautiful, but it's best to go off-season.
Otherwise the tourists ruin the whole atmosphere.