I own the JP and US releases of King of Fighters: Maximum Impact 2/2006 and I can tell you, right now, that there is a great leap forward between MI and MI2.

The voice acting is better. Not by much, but better. Especially on the parts of Kyo, Ryo, Alba and Soiree. All in all, you really get into the characters a bit more. This also has to do with the fact that now... ALL of the initially selectable characters have a story and greater interaction between them. On the topic of voices in KOF MI2, if you don't like the English or are a complete and utter anal-retentive purist, there is a dual audio and subtitling option. Although, expect the classic SNKPlaymore localization. *lol*

The gameplay itself and the visuals is where this game BLOWS it's predecessor out of the freaking water. Tighter controls, new systems like Sabaki/Hi and Lo Parrying, improved sidestepping and "bread-and-butter" combos (i.e. C ---> any special or DM), new Specials and DM's for EVERY returning character... This game must be seen to be believed. Speaking of which, love it or not, Falcoon has really gone the extra mile with his attention to detail on the character models and each one of their 16 outfits/color variations shows this. Need any more info, just ask.

Note: To unlock the Kick Commander, simply beat the Story Mode once (I think it's once) with any character.