Angry Birds hasn't been my most favorite game, and I always wondered what my friends found amazing in it. But I always did download every iteration of the game including Rio and Space. I think the best I liked was the Star Wars version, which got me to play the game a little more, obviously because of the movie influence.
They all are pretty similar, but probably the space one, I love how it circles and orbits and stuff. It's more trickier but more fun. I like all the Angry Bird games, but I preferably like this one the best.
It's definitely Angry Birds: Star Wars. There is nothing special about that, but perhaps my penchant for Star Wars is the reason why I ate it do high.
I like this one the best too second to the original. I've gotten to try some of the others and I did really like the circular movements as added challenges. The other ones seems to only add on the the themes instead of mechanics, but admittedly I only played the earlier levels so I might just have missed the innovations.