The pose of the characters is much like in super mario NES version or something.
Now I wanna see them animated! XD It's such a great idea, suprised I haven't seen it before now. Simple but effective, Congrats!
Awesome! Maybe Ryu and Ken can find some Hadouken Flowers inside some blocks. 
Have M. Bison inside every castle...
Dhalsim: "Thank you Ryu. But Chun-Li is in another castle!"
Ryu: >:(
As soon as I saw the preview icon - I knew I was going to be faving this. You really have done a superb job on these characters.
I don't normally fave things as simple as this but I got to here. Two of my favorite things (Street Fighter and the original Super Mario games, none of that later 3d crap) that I never thought would work together but you've pulled it off nicely. Every character is recognisable and has detail without overdoing it. The only thing I would change is that the 'red' on characters like Ryu and Zangief looks a bit orangey. I'd try using the red you've got on Ken's suit for those and see what it looks like.
excellent! they are all very recognizable ... with that "mustach", zanghif looks like one of those 19th century strongest men ^^
Great style! But Nes can use three color (except alpha-channel) on sprite only.