Right, let's see...
1st place - Gollum. Nice textured base, use of multiple modelling materials, but if Oz is anything like the UK, the bases aren't taken into account when judging, so that's irrelevant... It's a nice piece, although the blood doesn't look very real, and his eyes are a bit funny.
2nd place - Dwarf King. Again, scenic base, nice, but not part of the criteria. The axe, has very obviously been given a wash with Devlan Mud or Badab Black. If you look closely, you can see that this has dried in the axe head, where the holes are. Unless they aren't holes, and I'm spraffing, but that's what it looks like. There is some very neat freehand around the trim of the cloak, and, I think that, if the painter can do that, then they really should have made an attempt at the eyes. It's always said that the face is the focal point of a model, and this is very important with Dwarves, as a lot of this area is generally obscured by beard. Speaking of which, other than the white patch, there doesn't seem to be any evidence of highlights at all, which is inexcusable.
3rd place - Gandalf. Scenic base, very well done, but not counted. A very clean miniature painted in subdued tones. The blue sheen to the sword is overdone (whether or not there are Orcs nearby) and the front of the hat seems a little flat. This may or may not be the sculpt or overzealous cleaning. The texture of the beard is well defined, and the robes are very well done. Bar the sword, I can't really find fault with this mini.
Overall, Gandalf is the mode that impresses me most, and would have been my choice for First place.
Now, to answer your question.
If I was looking solely at the pictures in the thread, and the 3 winners, I'd say no. You have a very distinctive layering technique, which I find pleasing, thinking Kev Dallimore/ Dave Andrews style here, but I don't think it's what wins GD's. Also, the freehand on the banner is 'chunky' but I'm aware that it's 3 years old, and can see you have progressed since then.
I had a look at your other pics and I'm well impressed with those. Particularly the Scouts and the Space Marine Captain.
The Captain would be the model I think would do best, although, it could do with having the gun barrels drilled out, some additional highlighting on the Stormbolter strap and barrels, and more work on the cloak. As it stands at the moment, I think the cloak would be the models failing point, as the transition of colour is too sharp, and lacks definition, and the freehand pattern is rough. Now, by that, I mean it's a helluva lot better than anything I'll ever manage, but for true GD quality, it's just not up to standard. The base is fine as it is. There is some scenic detail, but AFAIK, bases aren't taken into account at all.
When I think GD standard, the names that stand out in my mind are Jacob Rune Neilson, Joe Hill, and Matt Parkes. Yes, there are others, but these guys work really sticks in my mind. And yes, most of them have been on the 'Eavy Metal team at one time or another. You don't need to be 'EM standard to win a GD, and there have been many occasions where the 'EM entries have lost out to normal guys work.
We have a local painter who is pretty good, he makes a lot of money doing commision work, selling painted armies, and pretty much cleans up at any painting competitions, but he's never been past the first stage of selection for a GD.
I think ultimately, you have shown the potential to do well, and the best way to answer your question I guess would be to enter next year.
That gives you just shy of 12 months to do the best you possibly can, and, hopefully walk away with something for the mantlepiece.