My gut reaction, which even surprises me, would be DAM Gangster Kingdom based on what has given me the most enjoyment in the last couple of years. But that figure line has probably nearly run its course, whether creatively or for financial reasons. So then I'd probably say, like many above, Phicen/TBL.
This is assuming that the question means, "collect from now on." If my entire existing collection of a lifetime had to vanish except for one single brand of items I could still collect, then my answer, unpopular as it may be, would have to be Hot Toys.