Hello there

I would like to know what other Action RPG's I can get for my DSi. I played both Zeldas (but stopped middleway because I got bored). All Castlevanias (a debate of the genre later) and Ys books I and II (wich were excellent games).

Are there other games with similar gameplay? thanks in advance

Well I am going to say you should try out unique experience of The World Ends With You, and maybe look into the new Lufia game that is coming out. 

Another game you might want to look into, and possible "try" is Summon Night: Twin Age. 

not a pure action RPG, more of JRPG with action elements is Chrono Trigger, one of my favourite games on the DS.

I second Chrono Trigger.

Chrono Trigger is not an Action RPG, The World Ends With You is my favorite DS game, and you might also want to consider Kingdom Hearts.

kingdom hearts 358/2... though I don't like that game... lots of people do. It is an Action RPG

The World Ends With You... I absolutely love this game my favorite game this gen... It's an Action RPG... but it's not exactly normal as you do go to a battle screen. There's normally a mini-puzzle you do at the top screen with your left hind, while using the stylus to shoot/stab/cut etc the bad guy. Hard to explain, but really unique.

Chrono Trigger... is really pushing your description... and you've no doubt heard of it. It's good though, but not really what you asked.

you've probably heard of all those anyways.

I don't play many ds games... can't be the most help.

I played Chrono Trigger on SNES so I don't plan to get it for DS

I will get TWEWY, looking very interesting. Maybe Avalon code as well

Dragon Quest Heroes: Rocket Slime.  It's pretty easily the best Zelda clone on DS, and personally I like it more than DS Zeldas themselves.

The Final Fantasy Crystal Chronicles DS games (Ring of Fates and Echoes of Time) are both solid loot 'em ups / dungeon crawlers with some great puzzles and a surprising amount of platforming.  

There's some decent looking games coming up too, Lufia: Curse of the Sinistrals in October, Okamiden next spring and Project Coda (aka: Solarobo) sometime hopefully.

I will consider Ring of Fates in the future.

And I'm definitely waiting for Lufia. I played all the games on SNES and GB/GBA (although Lufia 4 bored me to hell) and the DS remake/re-imagine looks awesome

TWEWY is amazing, I can't recommend it enough