There are really no good hotels by the EZE airport (if that's where your flight is coming into and/or leaving from).

While some hotel rates may include a free transfer to/from the hotel, most hotels in Buenos Aires do not offer such a facility on most rates.

To save some money to get from the airport to the hotel and back, there's the Manuel Tienda Leon bus/transfer option. http://www.tiendaleon.com.ar/prehome.asp?flash=S