Obama can do a good or bad job within the actual limits of the presidency. When has Obama let the limits of the Presidency get in the way of his doing something he wanted to do?
An even bigger question is when has the Congress ever stopped Obama from exceeding his presidential powers?
There was a thread earlier today in which the Democrats came right out and blatantly said (slight paraphrase): "If you don't let the president do exactly what he wants, then he'll just go and do exactly what he wants."
It's called dictatorship.