I have beenn playing the gotham games since they were metropolis street racer on the dream cast. They thrive on teh fact that they are about style, aswell as speed. The Kudos system and chaining mad slides and drifts together make for a very entertaining style of driving game. Now PGR4 is here, more of the same, but better on the 360.
Now there are also bikes, and you have even more style options such as this wave tot hte crowd.
Even stationaru things look pretty good
They have also mixed in the old and the new. I got to drive this around the old Nurbergring in this old maserati in the snow. A fantastic experience for a driving game
Things like weather effects are quite important to the atmosphere, puddles of standing water feel rock solid as you hit them and get a rumble pack jolt.
The music is pretty cool too, I enjoyed razzing around in a scooby with Ruby by the Kaiser chiefs, and Our velocity by Maximo Park blasting out.
Some of the car damage is also quite subtle, look at the scratches on the side of this one
So yes Halo is good, but so is this :-) I need to play online now I have a few miles under my sparco belt, but no reason to think it will be a bad experience :-)
Subtle little extras I have seen, Geometry Wars in the garage again, a new wave based version. Also you can upload shots to share with people. If you wander around your garage the walls will get populated randomly with other peoples photos of car incidents. You can walk up to them and vote on them. Nice touch for serendity and Web 2.0 there.