Agree with what touch said, there's not really such a thing as a 'good time' since everyone is at a different stage.
I started running about 3 months ago and could only manage about 3km in about 20 minutes but that was a 'good time' (6:30 per km) for me as I hadn't run for years.
Last weekend I ran a half marathon (21km) in 1hr 54mins so have built up to running 7 times further than when I started and averaging less than 5:30 per km.
I was pretty pleased but to give some context, the winner finished in 1hr 4mins so my time then looks very very average despite being faster than the average person in that race.
Times are pretty meaningless to anyone else so by all means post yours if you want people to say well done but ultimately your only real measure is your own progress. My current goals are to run 5km in under 20 mins, 10km under 45 mins and 21km under 1hr 45 mins but they're my goals not some official standard that would make me a good runner.
On a side note, the best advice I ever got for running was to focus on a smooth, easy style. If you can't hold a conversation then you're going to fast and should slow down. This way you can build both speed and distance and avoid injury (at least for a while, running is great exercise but pretty tough on your body). Also, get yourself into audiobooks, makes the time fly by and gives you motivation to go running on days where you otherwise don't want to.