My personal favorite is Showcase, on Av. Monroe and Arrebenos in Belgrano.
I like it 'cause:
1) It's pretty easy to get to by bus or train (linea mitre, est. Belgrano), and they have most current movies showing.
2) It's close to "Chinatown" so a movie can be combined with a cheap chinese dinner.
My current favorite Peruvian restaurant "LaCumma" is only a few blocks away on Olazabel y Arrebenos, as well as "Lotus" (Thai) and "Hong Kong Style" (Montanesas y Juramento - Very good Dim Sum!)
Another pretty good parilla is "Pobre Luis", on Arrebenos just a block or two south of Showcase.
Saludos,
David