I just got the game today, and it's pretty sick. The graphics are the best I've ever seen in any video game. It feels like a real boxing match, it's pretty crazy. It's different from round 3, so it takes some getting used. I was playing for like 4 straight hours lol. The game does a good job of emulating how the boxer fights in real life. I'm gonna start the legacy mode tomorrow.
My only problem is that they seem to put too much stock in to counter punching. From what I've seen, it's the only way to knock a boxer out. Ex. I was fighting against Manny Pacquiao with Miguel Cotto, and I dominated him most of the fight. All of a sudden, he gets a couple of counter punches in the 8th round, and he knocks me out. Kind of annoying, but it's probably something you get used to. Also, they really underrated Mike Tyson. They didn't do a good job of representing just how beastly he was. They made himm too slow, just not as good as he should be.
I only played for a couple hours, but I defenitely recommend it. It's got one of the biggest rosters I've ever seen in a boxing game. Great game.