I've contributed a few translation patches to ROMHacking.net, with a new one coming soon (an NES game, no less).
Some
amazing work comes out of that site.
But those README files don't really replace the manual. They help, of course, but even the longest and most detailed ones omit things sometimes (especially plot and context), or give things away the original manual wouldn't have done. Some of them are near-walkthroughs!
EDIT: BTW when I was writing that earlier post, I was thinking of Bokosuka Wars. 100% playable in English, but it seems like some bizarro-world attempt at a game if you don't know what's going on. (It may still seem that way once you
do know what's going on, but...)