Just a quick video to show that Angry Birds is available on Windows Phone 8. Of course, it runs really smooth, even on the Lumia 822 lower resolution screen. I played this on my Droid a year or more ago and the game ran great then on the lower processor speed.
So if you like the original Angry Birds, you won't loose it if you move to Windows Phone 8. Of course, you might loose all your saved games and scores!