Back when Alien vs. Predator came out on the Jaguar, I made complete maps on graph paper for every level and air duct, complete with exit names, item locations - the works.

Nowadays, I still take the occasional note for a game that doesn't have a FAQ or walkthrough. For my Surging Aura review, I wrote down each charm, its cast time, etc. and took about 2 pages of notes overall. I did the same for Pier Solar and other recently released RPGs.

GameFaqs and the internet are great, but not every game has been covered, and not all that have are complete.