Too bad this was on Jaguar and more werent made for future consoles.
No matter who you decide to play as the game is never boring and has so much to offer. From large levels to many different weapons. As the marine you have to gather different card keys to advance to different levels in order to escape in an escape pod. On the way you attacked by hords of aliens protecting the Queen or invisible Predators hunting for your skull. You can use a tracking devise to see movement around you and collect stronger weapons. Also what I thought was a great idea was that you can also move in the ventilation system, but be carefull as some have aliens inside. You never know what you will encounter when you enter new areas or different floors. makes the game very challenging and fun.
Playing as the Predator or Alien just enhances the fun aspect of the game as you can just wander around hunting humans for sport. When you die as an alien you just become the next closest alien and begin hunting again.
Too bad this game was lost in the Jaguar as it was definately fun to play and one of the best FPS around. Give it a try if you can still find it.