its hinted at many times that had Anakin survived Mustafa unscathed that he'd be a good fight for the Emperor. Based on that idea alone id say he could beat the brothers with difficulty.
You can't really take his fight against Obi Wan as a low showing, he was conflicted fighting his old Master, Obi Wan knew intimately how Anakin fought and Soresu was a perfect matchup against Anakins fighting style... Even with all that against him Anakin had Obi Wan on the ropes until he stupidly tried to jump over him and got mutilated.