Wonderware was first to market with a Windows based MMI which means it has a large installed base with many happy and loyal users. WW more or less set the standard that all others followed. The biggest drawback as I see is the need to script just about all animations in WW's proprietary language. Comments I have read suggest that the company itself is no longer the customer friendly entity of old since it's purchase by Invensys.
Following close behind was Intellution. The first generations of FIX were a more stable than their equivalent Wonderware product of the time and seemed on an unstoppable rise to domination until they released iFix. I am not certain why but it appears that the radical changes in this system alienated a lot of their customer base and they have wilted since. Again the purchase of Intellution by GE seems to have been more to serve the corporate's agenda than to the benefit of the customers.
At the outset Rockwell made the wrong decision not to do a Windows based MMI and stuck with the reliable but otherwise very dated DOS based ControlView for far too long and this product effectively knocked them right out of the market during the early 90's. Then they purchased a small independent which gave them the WinLinx and WInView products from which RSView32 and RSLinx were developed. Coming from behind these products have carved out a solid customer based and are now very mature, fully featured and reliable.
The next generation the RSView ME/SE product is not yet mature and although it's very powerful in some aspects (ie the FactoryTalk feature once you get it working). However I think it will be at least another major Rev or two before it is fully ready to take on the world.
Citech is the favourite of many. This Australian based company has an impressive product, in particular it pioneered the idea of Supergenies which hugely improved editing productivity. Lots of no extra cost drivers and a very customer focussed organisation Citech is no toy and can point to some VERY large installations running at very high performance.
The rest are the either also-rans, or minority products from small independents. Some are excellent in their own right but are not likely to be dominant in the near future. What the market is really waiting for is the next new thing, a disruptive product that changes the game.