UFC 3 is a fine single player game but it's multiplayer is tarnished with 3 big problems.
1. Server Instability - About 1/2 fights will be a disconnect and I know it's not me or my opponent doing it (being in party chat with them). Some fights have been laggy with up to a 1 second delay between button presses. There have also been times when I can't even connect to their content sharing system or leaderboards. The good news is that THQ says they are working on these issues and have been updating the community on an almost daily basis of what they are trying to do.
2. Even if the servers get fixed there are some overpowered moves that can be given to CAFs(Create-A-Fighters) and roster fighters possess. More details as to these moves and cheapness can be found here
Banned Moves in Leagues
3. Fix the glitch CAFs. It's been 3 games and yet there are still Glitched Super CAFs in this game. Here are a video and a post that show a super CAF at 256 and a how to make a glitch CAF at 106
106 Glitched CAF
There are some other problems but honestly these 3 problems are what is killing the online for this game unless you are in league.