Cuba has great healthcare for it's level of wealth but I'd be hesitant to call it world class. It lacks a lot of the high tech medical equipment that exists in more wealthy countries. If you have some rare form of cancer, for instance, you'll probably receive better care in the "west" than in Cuba. Assuming you can afford it that is.
What's important about Cuba is that they flex the healthcare resources that they do have entirely to what is best for its people, instead of what is best for corporations. Preventative medicine is incentivized in a socialized system while capitalist medicine would rather wait until you get sick enough to require a procedure that they can charge a lot for.
I can only imagine what level of healthcare Cuba would be able to provide if not for the crippling sanctions they have to endure.