A draw against an inferior team cannot be described as "great". Great is defined as: notable;remarkable;exceptionally outstanding. If yesterday's result was truly great then United would have to be the better team. As even a neutral knows that City is the better team even without Silva and Aguero there is no way to consider a draw against them great.
I do think that, in the grand scheme of things, a draw was all that was needed to keep pushing towards the title though. United absolutely had to win and they couldn't do it. City played it safe and got the point they needed. But at the level City are at right now, nothing less than a win can be considered great in any domestic competition.