IGN really has a 6-10 scale... and they suck at rating on that even. They're rubbish.
Forza 2 is a good game I feel, and after playing GT:HD, I'm leaning more towards FM2. My quick review is below...
Graphics, FM2 is quite stunning, though it is lacking in points. Things still don't look as real as they do in the GT series. I'm not sure why they don't, they just don't though. When using the hood view, the reflections off the hood of the car are distracting, and I have found that on tree happy tracks, such as the Nurb, trees will "pop" suddenly into existence on them. Other than these, its visually pleasing.
Physics feel fine, if not a little bit more oversteer happy than cars would be in real life. But I also did not spend much time fiddling with tires and it could just be FM2 defaults to a more grippy tire than you would find in real life. Plus side is FF cars are fun and interesting to drive; I enjoyed the Integra Type R quite a lot.
Control wise, simple and it works. HUD though is lacking in that the rearview mirror is only visible from the bumper view. I don't understand why they didn't make it visible from the hood view.
Sounds are good, though the tire noise still rubs me the wrong way. Another one of those things I can't explain, but it just doesn't feel right.
If I had a 360, I'd probably get the game and play it alot. Thats saying alot for me, since I buy about 2 games a year for my consoles. Online play looks promising, and possible updated content is a good thing, as long as they keep prices sane. And FM2 is actually in my list of games that are making me want to buy a 360, despite not having an Mk1 MR2 (or really any Toyota's for that matter... seriously, no Celica GT-4) or a challenging version of the Nurb.
So if you like cars and have a 360, get it. Thats what I have to say about it.