London doesn't have that romantic beauty that Paris exudes. The uniformity of the old buildings, the orderly little squares and gardens, the old-world charm of strolling along the Seine, the gothic churches at every turn.
London has been razed twice: in a multi-day fire in 1666, and during the Blitz in WWII. There's not a lot of architecture that has survived both events, so there are lots more new, modern buildings here. Because of this, it has a newness to it that radiates energy and innovation, rather than aesthetic beauty and charm.
Walking along the North bank of the Thames is always a treat, especially when the sun is low in the sky. In the right lighting, pretty much anything can be charming and pretty.