This is one of the "secret" reasons I left the Bay Area to return to Chicago - downtown Chicago (aka The Loop) is beautiful. Please help keep it a secret so everyone doesn't move here and drive the price of everything up. ;)
I do like the architectural diversity in the Loop, but it goes beyond just downtown. One of the things that I love about my neighborhood is how you'll find 2, 3, or 4 floor walkups built anywhere from 100 to 1 year ago right next to each other. Some of the modern architecture from the 60s and 70s doesn't look great in isolation and I wouldn't want an entire street of it, but when its sandwiched between a building built in 1920 and one built in the last few years it gives the neighborhood a lot of character.
The bay area has more than enough space too. It spreads over 100 kilometers south of San Francisco. It covers more than the surface area of NYC in total. The real issue is that the bay area refuses to grow. The population is only about 5 millions IIRC. The density is really low.
IMO, in order to accomodate more people, and deal with the insane rents, the bay area needs to start growing vertically. Every other urban area I've been to has towers, apartment complexes. Here everything is flat. Most apartment buildings are only two floors high, rarely more than three.
I won't get into the politics of all of this, but politics are the real problem. Many of the suburbanites around here want their suburbs to remain suburbs. The law of offer and demand should mean that apartment towers are getting built and rents go down as competition increase, but the regulations in place prevent this. Many swanky new condos are being built, but these are still flat buildings, not making efficient use of the available space.
Chicago has a dense transit infrastructure that spreads across the whole city, and pretty decent transit throughout the whole metro area.
Obviously, San Francisco is hemmed in by geography, but even if you compare the metro areas, Chicago is better suited to hosting large-scale companies than SFBA.
edit: an example: https://www.google.com/maps/@41.8970249,-87.6709707,3a,75y,9...