Can't really find a favorite between No More Heroes and MadWorld, Wii's most notable violent games. Both make pretty good use of the Motion Controls, both have an awesome sense of style and/or humor to their atmosphere, both protagonists are cool, both have a good soundtrack (this coming from a guy who normally doesn't even give a crap for hip-hop). For however many similarities they have conceptually, they have their distinctions in practice, though both also have a roughly equal number of what one does better than the other.
But if you're just asking if it's a good game, it really is an absolute classic. Admittedley, I'd take the PS2 version before the Wii version (I'm generally against the "wave the Wii-mote for EVERY melee attack" concept).
As far as MadWorld having "God-awful" AI, I'd have to disagree. I think I'd actually say NMH was the lesser of the two in terms of AI, what with the enemies being not only easier to take out, but less likely to attack (effectively at least).