"[In Fight Night Round 3], you often found that the gameplay degraded into two guys standing in front of each other and trading blows," says producer Brian Hayes. "You saw a very scripted, very repetitive experience where people stood in front of each other."
But the physics of Round 4 alleviate that issue, he explains in the video below. "What we're really trying to deliver is the most realistic simulation of the sport of boxing ever in a video game....Fight Night Round 4, you see a much more fluid, natural game."
For real. I only played the first Fight Night on the PS2. The trailers of Round 4 definitely look cool.