It's become a 2k franchise, not that it's contractually llmited as is the NFL case. EA helps this by fucking up Live, but 2k running out the same faulty approach every year without any real competition is just as lame as the Madden scenario.
That's what 2K's always done with it. It's what they did with NFL too.
VC's NBA 2K engine truly dates back to NBA Action 98 for the Sega Saturn/PC. It's like Call of Duty in that you can play the games in order and see how they've dabbled with it over time. I'm sure there's nothing left of it but even if you went 98->2K->2K3->2K6->etc. you'd notice the similarities and evolution in basic mechanics especially the animation handling.
EA's had the opposite problem in that they've scrapped and started new engines over and over, even when they didn't need to. Rather than doing anything incremental for more than a year or two. The best considered Live games historically were always second or third iterations of the engine.
Madden's had a bit of both as its issue over the years.
FLASH FACT: VC worked on the cancelled PS1/Saturn Madden 96 and were one of EA's sports developers before EA brought that all in house. After the cancellation, they did NHL 97 and split off, before landing in the warm bosom of Sega.