So, the main plot device in Back to the Future II (aside from the DeLorean) is Gray's Sports Almanac 1950-2000. As we're now in 2015, the statistics must be available, so my question is does the book (or at least a book very similar to that i.e. not necessarily that thin or by Gray's!) exist?
It is also unfeasible for any other sports almanac to exist that would cover 50 years and all sports. Bob Gale (Screenwriter) has this to say:
One of the things that nobody really paid much attention to, this is 50 years of sports statistics... it's kind of a thin book to cover that much,
According to the Wiki (forgive me) it was contemplated in an early draft that such a book would require around 5000 pages (Over 8 times as large as Harry Potter and the Deathly Hallows)
In an early draft of the sequel, it was contemplated that the almanac would have 5,000 pages, made out of a very thin (if not dustproof) type of paper available by the year 2000.
If you are looking for a modern day equivalent then it lies in something BTTF did not predict which is the Internet, at a cursory glance this website seems to feature all the information you'd want going back to 1936 (For college football at least).
Or at least only as a gimmick inspired by the film, not a real almanac.
In fact, all the references to any sports almanac 1950-2000 seem to be just related to Back to the Future props based on Gray's Sports Almanac.
On an unrelated note, there appears to be a musical composition entitled Gray's Sports Almanac, presumably also inspired by the Back to the Future films.