Welcome to gamerDNA, Melb. I'm glad you don't shy away from a good one on one fight. As a DS owner, I recommend you invest money in buying Bleach 2 for you DS from Japan (playasia.com). It is a great fighter game, and it supports single cart download play so your friends can play. And in case you didn't know (not assuming anything), the DS is region free so you can play Japanese games without a Japanese console. If you really like that game you might want to purchase the first Bleach game and Jump Ultimate stars. All 3 support the wi-fi network and you can play online, the best part being you can do 1 vs 1, 2vs2. (Also sidenote: Bleach 1 for the DS supports bots, and uneven fighting such as 3vs1, as a result though it compensates for the player to make it more fair by weakening your opponents so they deal exactly the same amount of damage to you based on how many people you are fighting. IE: If you are fighting 3 people and you are by yourself, their normal attack will do exactly 1/3 the damage of your normal attack. This balances out, because fighting 3 people at once can be challenging and fun, because they set up combos to make you flinch, one person can be attacking you (so you guard), and the other person shunpos to grab you, etc.)
Okay maybe I gave too much information, anyway; welcome to gamerDNA.