yeah phoenix wright simply has to be bought if you have a ds. if not, it's basically a hate crime against your ds. edgeworth ftw though.
and yeah, mario kart is good, playing it online against people you know simply awesome (dismissing chowden, mike7 and steveh of arfo/ex-otf fame so wise) but since i completed all the single player stuff i've barely touched it.
brain training is alright for playing a little bit every now and again. if you like sudokus then it'll keep you busy for a while, handy for having on commutes on trains and stuff if you're like me and have a 45 minute journey every day but i cba with it atm.
sonic rush is good but not earth shattering, probably can pick it up cheap so if you like sonic that's a good idea.
oh, and pes is coming out like next week or the week after, that might be good, especially with the wifi stuff.
and i doubt i'll get the chance to finish sonic rush first actually, would do it on the train to uni in a bit but i have to read through a chapter of a book on "transfer of properties between atmosphere and ocean"