Dungeon Explorer II is much better than the first one, and I say that as a fan of the first one. The quest is much longer, there are way more bosses and characters, the story and cinemas rule, and the soundtrack is ridiculously good. Personally, I'd say go for the US version because you won't get to experience the true awesomeness of the villain if you can't understand what he's saying. But if it costs too much these days, then yeah, go for the JP one.
Also, if you don't play the U.S. version, you'll miss the true femmasexuality of the the villian. He makes the WD Ghaleon sound like Mr T.
There's no reason not to buy both DE & DEII since they're both cheap and are two of the very best PCE/Turbo games around. If you play through the JP version of DEII and decide that a solid dub and translated text is worth it for you,
then buy the U.S. version.
As for starting multiplayer in DE, the way I remember it(to tired to set it up) is that when it asks "how many players?", everyone has to push and
hold their RUN button and
keep holding it until everyone who's going to play is doing it and
then everyone can let go.