LotR is a good point - and hmm, well, even in Japanese stuff it's all starting in print media? Or mostly, since most anime tend to start as manga. A lot of it is accidental, I think - very much like with LotR, the original story wasn't meant to be so epic, but then Tolkien tied it into his whole languages/world and the story grew to fill it. With a lot of fight shounen I think the epicness comes from trying to up the ante, make every battle more meaningful and emotional than the one before - so the scale and what's at stake tends to get bigger and bigger (in DB/DBZ, for example, it goes from saving his friends to saving the world to saving other worlds to saving the universe.) OP was more planned than most, though - as far as I can tell, Oda always had this epic story in mind (though I think it's grown more than even he was expecting...!)

Hmm, I don't think I've seen the "To the Sea" AMV? I stopped watching the OP anime somewhere near the beginning of W7 and only just got back into it this year...the vid's totally gone? SIGH!

Thanks for the other recs, though! ^^