So, I've been wanting both, since they each have select games.  The DS actually belongs to my gf and the PSP belongs to me.  We picked them up yesterday and have been enjoying them quite a lot.

So far we only bought 2 games for each: DS - FFIV and Pokemon Diamond . PSP - Final Fantasy and FF:Crisis Core.  As you can see, were avid RPG fans, but we don't only like RPGS.  I do plan on picking up the New Super Mario and God of War: CoO.

Enlighten me on what games are MUST HAVES and which I should stay FAR AWAY from, on both handhelds if you kindly would.

Thanks much!  ^_^

Dragon Quest IV (and soon V) for the DS :)

^ Oh yes, definitely getting those :P, gf wants them bad as do I.

Final Fantasy 3 on DS
Kingdom Hearts for both when they come out (they're different games)
And every DS owner should have Elite Beat Agents and the entire Phoenix Wright series

For DS, The World Ends With You, Chrono Trigger DS,.

For PSP, I can recommend the two Star Ocean games for it... Tales of Eternia, and FF Tactics War of the Lions.

Good to see people getting into Dragon Quest

Get Advance Wars.

Best turn-based tactics to date.

I'd get Breath of Fire III on PSP. You'd seem to like it.