Right up there with GTA
I enjoyed the storyline, and the voice acting was top notch. The head of the Saints Row gang's voice is the black dude from Men At Work (he was also in John Carpenter's They Live). His voice is awesome anyway, so was a good choice.
There are some pretty crazy car chases and things, and the city is well done. If there is one complaint, it would be that the lighting was not done well enough. Indoors was pretty cool, but outside day and night effects could have been allot better. I'm looking forward to Saits Row 2, which I think is out at the time I write this, but I haven't picked it up yet. I am also looking forward to finishing GTA IV.
A word of warning to parents. Saints Row is really raunchy and should not be played by children, IMHO. There are many descriptive/vulgar references to sexual acts, as well as strippers with pasties and the like. Also, the violence is way over the top. The game is replete with criminal activity. Definitely a game for adults.