It's a lot to do with expectations. I think just expect all famous places to be crowded and expensive, then you won't set yourself up for so much disappointment.
I didn't enjoy Venice or Florence at all because they were so very crowded, but I adore Rome, absolutely love it. I'm used to big city life and I found it very lively and manageable with the incredible bonus of phenomenal architecture everywhere you looked.
It also makes a big difference where you stay. I if you're in a cool hotel it's a lot easier to enjoy yourself than in a noisy, grubby backpackers.
I agree with the SAN Francisco comments. Stunningly beautiful but grimly depressing to see such a terrible scale of homelessness.
And the locals seem so affected and self consciously cool.
I prefer LA which is unashamedly weird lol
I don't understand the Grand Canyon comments though. I found it literally breathtakingly amazing.
Barcelona too, fabulous city..
And New York - absolutely love it. I'm used to big city life though and also love coffee and galleries so lots to enjoy in NYC.