I was surprised how much I enjoyed Ninja Gaiden: Dragon Sword on the DS today. The game was on the show floor over in Tecmo's booth. If you played through the incredibly short demo level you were given a poster, which I promptly discarded.
The title was very much a stylus game. You move around, jump and attack by tapping and swiping your stylus on the bottom screen. That sounds like it might be a bit annoying, but it wasn't. It's done in a way that makes you feel like you're doing a bit more than just mashing away at a button. For instance, a standard attack is performed by slashing down on a target. You can throw knives at your target by tapping on it and you can do a super attack of sorts by swiping up twice to double jump and then down to plunge a sword down into your target.
The demo was far too short to get a solid feel for how much fun it might be once you really dig into it, but from what I played it was quite a bit of fun.