Sonic Boom!

I played it finally, after getting it on the 20th November, I had to put it aside for school stuff.
I played it this weekend. Only on evenings, I had to prepare my presentation.
Well 2 evenings and im finished with the main story. Dont you think, too its kinda... Short?

SPOILER ALERT

I dont get the role of Shadow, he comes, we kick his ass and he falls into a portal into the future and appears at the end of the game after we defeated the end boss Lyric.
The future ''end of the game'' for us in this moment.
He comes up and says: ''I see you did all this by yourself'' (or something) and walks away with a smile?
WHAT??
Besides the fact his voice is in english AND german just ugly. All the others are super good and cool, i think that are mostly voices of Sonic X (german).

I think it was about 8 hours gameplay and I tried to find EVERYTHING. I stucked sometimes and even just ran around for hours and that thing was still too short.
They could have made more missions and quests etc in a level.
When I think about the fact that I spend 80 hours or something on Pokemon and Zelda it makes me sad.

Sonic Boom was awesome! I love the world of it, it was like in Wii games of Spyro.
Nice stages, nice races, all was good.
But why I finished it in 2 days only playing it at the evening? T_T Im no hardcore speed gamer, Im kinda lame and try to play slowly at games like this.

I plan to continue playing and finishing all missions. Maybe the game trolled me? I saw the credits ._.