Yeah, look at the comics. They're in anime format, and they show off the Mario Bros. at their worst looking. If anything, though, the next Mario Bros. movie should be animated. Not anime style, but at least in some animated style we can appreciate.
Real life actors wouldn't work so well since we know that developers can never find actors that even remotely look like what they're supposed to be.
Then again, do we really want an animated Mario movie? It would be like watching the Pokemon movie: It's either good or a disaster. Me? I don't see any way that a Mario movie can be good.
But what do you think would happen if different mascots from different franchises all teamed up in some movie to fight a whole bunch of evil from other franchises? For example, Mario and Sonic team up. They will be going up against Bowser and Dr. Robotnik as the villians. Then there are other characters that could be thrown in, like Link and Gannon, Samus and Ridley, Star Fox and Andross, etc.
To be a Koopa, you must become a Koopa.