I've played through a lot of Final Fantasy games over the years. The closest I've come to playing through them back to back, though, was when I played Final Fantasy IV, V and VI as soon as they were available during the 16-bit era.
Former game journo Justin Davis is planning to make that effort look like a "pfft"-worthy cakewalk over the lifetime of his new blog, finalfantasy sequence.com.
The point of Davis' blog: To follow his "chronological journey through the Final Fantasy franchise." Yes, that means he's planning to play, through completion, all 13 of the mainline Final Fantasy titles. (He has said that he may skip the MMO-ish 11th entry in the series, although he also has said that he's considering adding is-it-or-is-it-not-a-spin-off Final Fantasy X-2 to the mix.)
Davis has published just five posts thus far--all relating to his still-early playthrough of the original Final Fantasy--but it's already clear to me that his (hopefully) lengthy chronicle will be well worth following.