An excellent improvement over it's predecessor in almost every way, but more single-player content would've rocked. Read
The graphics in Tony Hawk's Downhill Jam are quite simply excellent. A lot of the levels have lots of interesting city backgrounds, overhang, and the cartoony visual style really adds to the overall vibe to make it extremely appealing. The menus are also an amazing improvement, building on the laid-back scribbly graffiti style as well. In addition to this, the trick and character animations have all been taken up a few notches, and the camera and frame-rate are all rock-solid. The sound is a much better improvement as well. There's actually songs worth listening to, the number of them has increased, the sound effects have been slightly tewaked, and the voices are on par with Sk8land (which were also excellent to begin with). Overall, an outstanding presentation with a much better soundtrack.
The gameplay has also been tweaked, with some points for the better and some points for the worse. For the negative points, you can no longer perform reverts or graffiti tags, and the number of manuals you can perform have dramatically decreased, which were all pretty much unneccisary. However, the double and triple tap moves have been improved, since you can now simply hold down the button to keep the board spinning. Also, the Bert Slides have been made easier to perform, and spinning and rotating seems more fluid.
The whole idea with Downhill Jam is to break away from the free-roam environments and thrash you down a steep incline like in SSX while going over 60 mph, and to execute it all while rockin' out and staying funky; and it manages to succeed as a whole, and the game is a blast to play to boot. But it's pretty obvious of it's influences, since a lot of the special tricks are incredibly similar to SSX's Uber Tricks, and the levels are designed in much the same fashion; not that those are both neccesarily bad things.
The bottom line is that this game is a blast to play, and it is only enhanced by the incredibly deep and engaging multi-player options, both online and local. The board and character designing, character animations, audio, and menus are all an excellent improvement over it's predecessor, and the cutscenes are also pretty cool. But although they are fairly large, there are only 6 tracks to race down, which was kind-of a downer, since they could get stale fairly quickly if you play it religiously like me. If you really loved Sk8land, you'll love this game even more, but you won't play Sk8land as much anymore, since they're both fairly similar in some respects. Overall, a great game; not as bad as everyone may say it is, GAMESPOT!