Other than the weather, nothing is great about it. The ocean water is cold as ice, too close to Mexico, girls are meh IMO. After a night in the Gaslamp district and a day at Coronado and LaJolla you've seen it all. It's just boring.
But there are very few large US cities that really stack up as awesome beyond the tourist locations. Taking some of the largest by population, I'd slot them like this in no particular order...
Awesome: Chicago, New York, San Fran, Austin, Boston
OK: New Orleans, Philly, Indy, Dallas, San Diego, Charlotte, DC, Baltimore, Seattle, Denver, San Anotnio, Miami, Portland
Suck: LA, Houston, Pheonix, Columbus (OH), Fort Worth, Detroit, El Paso, Memphis, Atlanta, San Jose
And yes, I've been to all of these for at least 5 days.