According to ESRB, this game contains: Animated Violence
True boxing fans should definitely stay away. I know the lineup in this games makes it extremely tempting, but the resulting game is a chore to play and will only disappoint.
Casual boxing fans dying to take on the boxing world as your favorite boxer should rent this game first. If you're dying for a boxing fix, then own the PlayStation version. The PlayStation version includes 50 boxers compared to the Nintendo 64's 25 and is a much truer simulation than the Nintendo 64 version. There are also key bonuses only available on the PlayStation like boxer bios, a 'classic fights' option and even a music video. Some of you may dig the ring babes in thong bikinis.
Arcade boxing fans should get a Dreamcast (if you don't already have one) and get Ready 2 Rumble.