@BluePhaze: I've never played Megaman so can't comment on that, and Mario - is that Mario Bros, Super Mario Bros or something else? I'm only familiar with the original Super Mario Bros on NES, and that game you can certainly fire up for a quick game. But there's an awful lot of levels, enemies, tactics you have to learn etc.
I think any game you can fire up for a quick blast is a casual game. Most coin-ops would fall into that category by that definition, as they want to kill you off in a couple of minutes so you have to insert more coins.
My 2c: Based on what I've seen in this thread, I would classify your app as casual.