I'll give 2K3 credit that it was a good first effort. It was the first game to have all 300+ D1 schools which was very cool (and put March Madness to shame). But there were no sliders and limited options. Missed layups were frustrating and I think this game had the jump steal bug.
2K4 was a nice improvement. I really enjoyed this version.
2K5 added a lot more momentum. Not sure if this one or 2K4 had the "Alphabet" bug where I think the conference tournament seedings where sometimes determined alphabetically instead of by the standings?? (my memory might be failing me on this one).
2k6 added the selection show.
2K7 was the one I didn't get. From what I read, it seemed pretty similiar to 2K6 (since they were also developing 2K7 for next gen). Although I think they fixed a few things like a stat glitch in 2k6 where a player would suddenly get credited with 10 missed FG's.
But yeah, great series. CHoops is probably my favorite sports franchise, and that is saying something as I am not really a big college hoops fan 11 months out of the year.