Nothing short of great
I think PGR4s best feature is its single player mode as i hear online isn't very good. The career mode is long and evloves around full rach seasons in which you go to each city and chose one of the 4 events avaible there. You start off ranked last and your job is to get losts of kudos and become the world no 1 rank. This will take about 3 seasons on normal but on hard the career mode will take alot longer. PGR4 feature a good selection of tracks from major cities all other the world and it also has many differnet types of events.
The bikes are a fun addtion but don't handle very well. There is a great sense of speed from them however bikes are amied at the kudos hunting players as you can do stunts like wheelies and stoppies on them.
The graphics in PGR4 are execellent and this shows in the car models and city backgrounds as well. the sound of the cars engines is very relistic and they all sound different.The soundtrack is rubbish though. the only thing that they should add in is damage for the cars because if you hit a wall at 200mph all you get is a scratch.
Overall PGR4 is tweaked and improved version of the one before it. the gameplays been refined and with great visuals. PGR4 is a great package racer which is a must by for racing fans and 360 owners alike.