flyingfox mentions Godzilla.
Last year I had a marathon of every Godzilla film (all of them in original Japanese with English subtitles-the best way to watch ANY Japanese film IMO). 28 Godzilla films (NO, I didn't include the tuna-eating U.S. embarrassment), plus Rodan, Mothra, King Kong Escapes, and Rebirth of Mothra 1, 2 AND 3. I also threw in the episodes of Zonefighter that featured Godzilla, the Daimajin trilogy (Daimajin, Daimajin Ikaru, & Daimajin Gyakushu), Frankenstein vs. Barugon (known by most as Frankenstein Conquers the World), The Mysterians, Varan the Unbelievable, War of the Gargantuas (which was originally intended to be a sequel to Frankenstein vs. Barugon).
Of course, this marathon took place over a 5 day period (I was unemployed at the time, so this explains the available FREE time...), but I remained faithful to it by refraining from watching anything else.
My wife didn't want anything to do with it (of course), but my two kids joined me every now & then (even though they didn't understand the Japanese & reading subtitles isn't really an option for a...then...4 & 9 year old).
~Paul W. Sondersted, Jr.