I'm starting to develop games in Flash CS5.5.
A few questions:
Please help me decide between:
- ActionScript 2.0
- ActionScript 3.0
- AIR
Any game suggestions?

Actionscript 3.0 is more powerful that 2.0, but a lot less easy to learn (scripts are put on individual frames instead of just on a movie clip).
Actionscript 2.0 is a lot easier to learn, but I'm not sure what the cap is on quality.
I don't understand AIR, it seems to be a very different thing from actionscript.
Overall, I think you should look at Actionscript 2 & 3 games and see the differences between them. Decide which will give you better control.