Though Sonic Generations is promising, I wouldn't get my hopes up too highly (although I myself have pre-ordered the game). This game has so many good things going for it, I would hate for all that to come crashing down with some gimmick that we will only be aware of once we start playing the released title.
When I saw Sonic Unleashed, I thought, "Yes! Finally, after all that Storybook games bull crap on the Wii, Sonic is back on top!" And for all of the Sonic Daytime stages, I was correct. You actually felt like Sonic has successfully crossed over in to the next generation of the 3D realm. Then I played the Werehog Nitetime stages, and I think I died a little inside; though not initially bad, they were NOT the Sonic stages that we had finished playing a few minutes ago. Half of a game was ruined, and that's what Sonic Unleashed will be remembered for the most.
It's like Sonic is in a race and he is just blazing through the entire track. The finish line is in sight, but before he crosses it, he trips on the Werehog stages, and falls flat on his face. He still manages to get up and win the race, but everyone will remember the fall much more than the victory.
Let's hope Generations changes this.