Istanbul is an excellent city for touristing. We spent five days there and each was full of the kind of sites and experiences of a Paris/London/Beijing tourist quality.
To speak of Istanbul as the crossroads between East and West is cliched and, to my mind, wrong. Istanbul feels primarily European, and I imagine that feeling is just going to increase over time. Plus, Istanbul’s geography is just a fraction of what makes it interesting. History, more so. It was capital of the Eastern Roman Empire, Byzantine Empire, and a range of Turkish empires that have followed. What that amounts to is a terrific collection of churches, palaces and mosques.