Viewsonic may have had good CRT monitors, but when you consider consumer level LCDs viewsonic does not have good models. Most consumer level (non professional) viewsonic monitors have mediocre reviews. When you check online reviews you'll see that viewsonic panels rarely shows up. But Samsung on other hand, is one of the largest LCD manufacturers in the world with many highly rated LCD monitors. And when you compare the market shares you'll notice that viewsonic doesn't even have a significant share in the global market.
Having said that, you can’t just say one brand is better over the other. You have to evaluate the quality based on the individual monitor model and its features. But if you just want to know which is the more popular LCD brand between the two, then its Samsung. No question about it.
Most here will say viewsonic is better based on their experiences with old CRT monitors. Remember guys, LCD and CRT monitors are worlds apart in technology. Having a good reputation for making CRT monitors doesn’t mean their LCD monitors are also good.