The Steak - It is cliche and everyone says it but there is a reason for this. The steak is incredible. Get a Lomo steak at a restaurant and you will never be disapointed. Is it really that good?! Yes. It's so good that if if you are a vegetarian you might want to pretend you are not when you visit.
The Service - The service at pretty much every restaurant, cafe, bus, ticket booth, etc is phenomenal. The people are friendly, they go out of their way to help you, and they offer a standard level of service far above anything we see in Canada.
The Coffee - 99% of cafes, restaurants, and even some little shops, have a fancy coffee maker and they know how to use it. Coffee also isn't just coffee here. If you order a coffee you'll always receive a little drink of juice, water, or soda water with it. Most likely you'll also get a few little treats too (cookies, sweets, etc).
The People - The people here are some of the nicest we've ran into in the world. There is always a smile, a laugh, and more often than not a joke. They are also incredibly patient as non-spanish speakers do their best to interact with them.
The Natural Beauty - This country is achingly beautiful. It is also amazingly diverse. Where Canada spreads across the globe mostly horizontally Argentina goes from north to south. In a span of just three days we saw monkeys in the jungle and penguins near the take off point to Antartica. Argentina has also provided us with two of the most awe-inspiring natural sights we have ever seen. Iguazu Falls in the north part of the country has pretty much guaranteed its role as the yardstick from which we will measure all waterfallls (Niagra is ugly and boring compared to it). Also, the glaciers in Patagonia took our breath away.