Great game in concept
It's just that Flash isn't a very good platform for long games like this. That said I enjoy all the work put into it, the depth of the voice acting and the length. I don't know how long all the other stages will be but this game must be massive, not to mention all the different little mini-games. On par with old SNES platformers and brawlers, and that's what I think you were going for.
That said, fighting enemies was pretty frustrating, especially coming back to a screen to find everything respawned when I stepped out for just a moment. Because of that it's very unrewarding to fight enemies and I found myself just running past them. Other then that my only problem is the graphics.
I'm sure that it would be difficult to get high quality art for such a long and expansive game (from what I see each stage has new tiles, enemies, people etc.) but right now it's the only barrier keeping your game from connecting better with people IMO. Your sprites and backgrounds are very flat and dull, and I think it takes away from the experience. Riding through the tundra on snowmobile shooting at other bikers was awesome, but it would be even more awesome if the art was detailed and immersive, to an extent.
Not a bad game by any means it's just that improved graphics would add so much to it. Maybe start practicing for your next game, read an art book or something?