Cutting to the chase, UFC: Undisputed looks fantastic. All of the fighters look just like they would on TV. This is one of those games that knows what it wants to do and simply does it. The photo realism works out great with the fluid movements and excellent collision detection. The problem with a lot of games based on full contact sports is that they don't look entirely convincing when two different sized characters collide. UFC: Undisputed doesn't have any problems with anything like that. Every punch connects, every kick lands, and every grapple makes full contact so you don't have to concentrate on anything except your strategy.
Most sports games have announcers that record lines to use in their games so it sounds more like the real thing. Either I wasn't paying enough attention or the announcers recorded a few thousand lines of dialogue because I honestly didn't hear any repeat lines (except when I replayed a match I lost.) Each match-up seems like it has unique commentary and each situation and fight has an individual audio conclusion.
A soundtrack plays during training and Menu screens and while the ambient stuff sounds cool, the licensed songs are from at least 5 years ago. The music is hyper-macho with plenty of hard rock and rap-metal to appeal to their core audience. There were a few songs I liked, but I couldn't find anywhere that listed any of the tracks, so I had to resort to the guessing game, but I know I could hear FLAW if anyone even knows who they are anymore.
