For those of you who are worried that Pfizer will lose a large chunk of its Viagra sales in the near future, you can rest assured that it will not. Moreover, Pfizer is busy developing newer drugs and they will contribute to its revenues as well. At a 4.75 PEG ratio, Pfizer is certainly in the overvalued territory, but it has very impressive profitability numbers. With a profit margin of 27% and an operating margin of 32%, this stock will prove to be a good long-term buy.