KZ2 had some of the greatest multiplayer aspects, but the fact that it felt like you were wading in jello, and a few balancing issues, kept it from being the greatest. 32 Players was awesome as well, it felt like a faster-paced Bad Company 2, but it had it's problems in the smaller maps.
KZ3 fixes all of these by not making TDM and Warzone such a clusterf*, but still having a good amount of players on either side. Guerilla also seemed to have learned a lot from the private beta, but we'll see how well they did in the upcoming Public Beta on February 2nd.
BTW: can someone who got in the KZ3 beta tell me; did they fix the rocket wh*res in KZ2? Nothing like defending the assassination target for 59 seconds before some kamikaze assault comes bursting in at the speed of light to ruin all the hard work.