Ben Smith, Folau and Mike Brown are the best, if I was picking one I think I would choose Smith. After that, very hard to decide, so many options but I do think Halfpenny is over-rated, wouldn't be in a top ten of mine.
Could not have put it better myself
For me Smith, Folau and Brown are clearly the top 3 fullbacks in world rugby. It is quite difficult to compare Smith to the others though given he hasn't been given the chance to play 15 for the All Blacks (through no fault of his own!). He was the outstanding wing in test rugby last season, and was close to winning world player of the year. However he is a better fullback than a wing. A much better fullback. He was New Zealand's Super Rugby player of the year at fullback for the Highlanders, and at times for the Highlanders over the last few seasons he has looked at a completely different level than the other 29 players on the park. Hopefully the AB's selectors will give him a shot at fullback this season, and the rest of the world will find out just how good he is!
Folau is the best attacking fullback in world rugby and is phenomenal in the air, but he isn't the complete fullback that Brown and Smith are. He still needs to work on his defense, work-rate and positional play. In saying that he still has a good claim for the number 1 spot as he is an incredible weapon with ball in hand. Mike Brown in many ways reminds me of Ben Smith. He doesn't seem like the quickest or strongest guy around but he had a deceptive ability to break the line, and always seems to make the right decision. It would be great if the AB's selectors picked Ben Smith at fullback against England as the match-up between Brown and Smith would be a real highlight.
I'm not surprised Le Roux is rated quite highly by many, but I do think he is a tad over-rated. Don't get me wrong I love watching Le Roux play (he is probably my favourite South African back to watch), but he does have a few flaws. He is probably the most creative fullback in world rugby - his passing game is phenomenal - but at times I feel he tries to do too much, hence his error rate is usually very high. He has a good kicking game, but I feel he kicks the ball far too much (he is currently equal 1st in kicks made in the competition with 53). The biggest issue I have with Le Roux is his defensive ability. He is a very poor defender - he literally only makes around 50% of his tackles.
Optastats have him making 15/27 (56%), while
Foxsports.com.au have him making only 12/26 (46%). That really isn't good enough for a test fullback in my opinion. This is not to say that I wouldn't pick him for the Boks - I definitely would as I think what he brings to the side out-weigh his poor defense, I just wouldn't rate him in the top 5 fullback in world rugby at the moment though.
Below the top 3 I would include the likes of Halfpenny, Hogg, and Israel Dagg. I've never been a big fan of Dagg (and he is in poor form at the moment), but he is an experienced international fullback, and his ability under the high-ball and massive punt is a huge asset at test level (though not as much at Super Rugby level).