I have finished the 4 games,1 and 3 being the best,IMO.
Yep,its a battle of logic and wits with the other prossecutors,but the thing is,for each case,everything just gets more epic.(If you played cases 4 and 5 from the first game,4 from the second,ALL from the third and the 4 from the fourth,you should know what I mean.)
Also,the games count with the most evil Masterminds ever (Some of them may be accidental,but in the spoiler there are the truly evil ones) Dahlia Hawthorne,Matt Engarde,Damon Gant,Manfred Von Karma,Kristoph Gavin,Luke Atmey,Morgan Fey....Just to name a few
Phoenix and Edgeworth are the best rivals I have seen in handheld games so far,and almost every moment of the game is packed with a lighthearted touch of comedy that will make you laugh for the sake of it lol
Also,the first game made me cry at one moment Lana and Ema being reunited after that long ordeal of 3 days in Court
So,I gotta say,these are some of the best games,ever.Also,they exercise the brain,with that all logic and rational thinking :P