The best piece of code I ever wrote in my life was nearly 100x faster than the next best algorithm ever written to do that problem. That took the expected run time down from a few days to an hour.
It was not a particularly well-commented piece of code. If it were, it would have been even better.
It was not a particularly obvious algorithm for solving the problem. If it were more obvious why one would choose to do it this way, it would have been even better.
If the primary concern is runtime (because it normally takes days to run), and you literally make it orders of magnitude faster, that's good code. It could be better if it were also better commented and easier to maintain, but those aren't *always* the primary concern (yes, sometimes they are. That's the point -- criteria differ!)