Maybe best jrpgs but western rpgs offer quite a few things that haven't been matched yet by Japanese developers. Maybe one day they'll have their mass effect or elder scrolls equivalents but I don't think they will anytime soon.
I've never played the Mass Effect games, so I can't comment on that, but I've always found Elder Scrolls to be a bit "dry" at best. Just way too much sandbox for me. Plus, as huge as the games are, the variety equipment-wise is just not there. I like seeing all kinds of different armor and weapons and what they look like, but most of the stuff in Elder Scrolls is either not that different, or just stuff you've upgraded. I'd appreciate something more along the lines of available armor and weapons you find in the recent Fallout games.
Edit: And to the people giving Neptunia -your mother is a classy lady-, what were you expecting? Lol. Its fun just because its a silly funny little game. Its not meant to have some massively epic story full of srs bzns. Its all about lulz and fanservice. I also found the sheer amount of game and anime references they fit in to be quite impressive.