I preferred 1 & 2 over 3 as I liked the fact that it was just one level after another, no map or overall adventure. I think I prefer 1 over 2 merely because it's simpler. Is there going to be a Shift 4?
Yes, there is a shift 4 coming (I think John said it somewhere)
Now, they all have good storyline. I don't like how 3 kind of left you hanging. Also, though I figured it out after a while, the newspapers were a hassle. The level builder and all the achievements were cool.
I noticed that shift one wasn't grid-based. That's a plus for it.
Shift 2 was fun, and simple. Also, it had good unlockables.
Hmmm...soooo hard...I'm gonna say a tie between 2 & 3