I should have been a boxer…
I picked up Fight Night Round 3 for the PS3 yesterday after a brief preview the other night.
I can’t remember when I’ve had this much fun. Now that I’ve beat a number, like 30, computer opponents and my son a couple times. Perhaps I’ll have to try it online 
The last boxing game I played (test runs with Wii boxing don’t count) was the original “Punch-Out” (see Wikipedia) arcade game. 
This is far superior as you might expect.
You can jump into the ring in any weight class and pair any two boxers. Additionally career mode is a ton of fun. The training section (and you need to train for every fight) is a tad weak. But it’s a blast to play.
I highly recommend this game, even if fighting isn’t your style.