I think Kirk is sloppy as hell as of recent years...After the Black album he slowly became consumed by his Wah. For this I can see why people think he may suck. Metallica as a whole is not known for being overly complicated at all, but Kirk's solo's often fit the song 100% perfectly. Especially from RTL through to the Black album, even Load - Reload, although very bluesy and many repeated phrases they still fit the song and rhythm section perfectly for the most part.
Randy & Jimmy - can't deny their rock God status!