This game wasn't as good as Smackdown vs. Raw 2007 but it is still worth puchursing and playing.
There are 8 fighting styles in the game each with their own special moves and abilities. Good examples are High-flyers can do springboard attacks and sneaky pins and superstars with the Hardcore fighting style can use extra weapon attacks and even make themselves bleed, there are many other fighting styles each with their own moves. When in matches, superstars have 2 fighting styles each. You also get shown video clips, before the game, showing you how to use the fighting style moves.
Another new feature in Smackdown vs. Raw 2008 is the struggle submission system, when you do a struggle submission (e.g. Anaconda Vice) you move the right analog stick to apply pressure but you can for only a certain amount of time. You can stop applying pressure so you can make the submission last longer but it also gives the opponent a chance to escape, just like on the WWE TV shows.
The Create a Superstar mode has improved, having more options of clothing you can put on your superstar. The created superstars also look a little bit more realistic.
Most of the main superstars are playable but there is a few that should have been included but they weren't. Rob Van Dam isn't even in it, which I found a big disappointment. Some of the superstars look exactly the same as in 2007. Umaga's entrance is exactly the same as 2007!
The new 24/7 mode is a good idea. You do different things every day that can raise your popularity, your stats and if you are not careful injure you. There is Superstar Mode (play as WWE Superstar) Created Superstar Mode (same as superstar but you have to do extra shows on heat first) and GM mode (play as General Manager of a brand).
General Manager Mode can be a pain because the other brands will more likely get most of the best superstars before you even have a chance but it is still worth having a shot playing.
Superstar mode is quite good, it isn't as good as 2007 but the fact you do things every day is great.
The controls have changed a bit. Finishing moves were usually L1 now it is Triangle and running is holding L1 and moving left analog stick in the direction you want to go. One other problem is that there are less Strong Grapple moves and Ultimate Control moves. They could have done better and some environmental hotspots are no longer there.
Smackdown vs. Raw 2008 wasn't as good as Smackdown vs. Raw 2007 but it is still worth purchasing and playing.