Phoenix Wright. Very cool.

That would be Pokemon White, though Black is much cooler. And a few suggestions would probably be anything from the mainline Pokemon series (DPP, HGSS, BW). Pokemon always defines Nintendo handhelds, especially if you don't want Mario (and something tells me you wouldn't love Nintendogs or Brain Age, either).

hehe you'd be right. On the grounds that dogs actually scare me ( I know the ones on Nintendogs aren't scary but you get the idea) and I own Brain Age/training for PSN.

Additionally, it seems getting DS games 2nd hand for cheap is incredibly rare, all these games I'm looking at are coming up £20-30 a piece :(

and Ghost Trick!

These are my favourite DS games:

Top of the list are the Ace Attorney (Phoenix Wright) and Professor Layton series.

I love good old click & point adventures, which is why I really like Secret Files: Tunguska.

Art Academy is a great painting "game". I was never personally interested in painting and thought I'd completely suck at it, but when I gave Art Academy a try I was really astonished by myself what great pictures I could paint after just 2-3 hours of Art Academy.

Picross is a really great game too, Very addictive.

From my collection, I'm going to tell you a few games which no DS owner should go without! (That are not Mario or Sonic)

- Pokemon: Black/White (In my opinion, the second best Pokemon games (after Gold/Silver))

- Elite Beat Agents (A bit different. It's an epic rhythm-action game that is super awesome xD)

- Fire Emblem: Shadow Dragon (Amazing TBS greatness.)

- The Ace Attorney series (A collection of very fun court-based dramas) 

- Chrono Trigger (A must, especially if you haven't played the original)

- Professor Layton series (I recommend all 3 of them, but I think they get better as the series goes along)

- Advance Wars (Two of these - Days of Ruin/Dark Conflict is the best one. Will keep you busy for a long time)

- TWEWY (Probably the best material that SE has produced in a long time.)

- LoZ: PH/ LoZ ST (Great titles, with a lot of content and a fun story)

- Mario and Luigi series (I know that it's a Mario title, but they are hilarious, and unmissable. Play these!)

If you only play one DS game in your life, make it Tokyo Beat Down.

Any good SRPGs on the DS? This is really the genre I tap my vain for.

Front Mission!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

There's one reason why I keep my DS Lite instead of selling it in favor of a 3DS:  It's the best damn GBA player in my house!!  Hang on to it and occasionally, tell it you love it.  It won't get weird.