As CC says, Colombia is a country of many (very different) cities.
About Bogota, I lived there for 2 years, and found it to be fairly unpleasant - terrible weather (cold, wet, windy), too high for comfort, and even being situated on an altiplano where logically all the rainwater must flow away, they manage to have knee-high flooding in the streets. Traffic is awful (no metro system), and there's relatively little to see. Colombians from other cities simply refer to Bogota as "the fridge" or "la nevera" - cold damp and dark.
At least living there motivated me to see other parts of Colombia, it was almost a mental-health necessity to get out of there:
I've been to Medellin many times, I was impressed with it at first, but as time went on and Colombia became more affluent, it started to have major air contamination and traffic problems. Nice enough weather, too far from any beaches, I didn't like the expat vibe, centered on El Poblado and Parque Lleras, all gringos chasing paisas. It is a major business centre, though, and has a decent municipal railway.
Cali is nice for a weekend, but there's nothing much to keep you there.
I much preferred the coast, especially Cartagena, the walled city, and the island archipelagos off the coast. It's extremely touristed, both internal and international. It's also got a very hard-sell vibe on the beaches, but that's avoided by going to more remote beaches or the islands. There are lots of property investment opportunities there, now mostly outside Bocagrande, which is full, and tourism is year-round. Some of the smaller cities are also quite nice, like Santa Marta, but much quieter. Barranquilla is just too hot and humid to consider living in.
