Resolve to keep your portfolio healthy: Help us pick the worst stock for 2008.

I cringe as I anoint Pfizer (NYSE: PFE), which has done such good work for humanity, as a "worst stock," so I'll preface everything I say by noting that a "worst stock" is not anything close to meaning worst company, at least in the pharma and biotech sectors. The worst drugmaker distinction would go to Neurochem (Nasdaq: NRMX) or Telik (Nasdaq: TELK) -- both one-star CAPS stocks, by the way.

Even though the pharmaceutical and biotech sectors are some of the best sectors for investors to be in during a recession (and we are in one, even if the economic data hasn't caught up yet), Pfizer has to be tagged with the "worst stock" label because it's the least appetizing of the big pharmas for several reasons.

I'm not going to spend much time discussing the upcoming turn-of-the-decade event for Pfizer's lead drug, Lipitor. That's been done ad nauseam. It's worth pointing out, though, for those expecting a few more strong years for Lipitor, that the drug's sales erosion is already under way because of increasing competition from other generic and branded statins. Sales of the cholesterol-lowering drug fell 5% year over year in the third quarter last year. Five percent may not sound like much, but that translates into hundreds of millions of dollars in reduced sales annually.

Any analyst could point to the decline or failure of individual drugs with a large pharma such as Pfizer, Merck (NYSE: MRK), or GlaxoSmithKline (NYSE: GSK) and paint a picture that makes the company's future look prettier or uglier than it really is. The more important theme, though, is that Pfizer's pipeline is extremely weak in regard to new molecular entities, and most of its phase 3 drug candidates are label expansions of already approved compounds.

A drugmaker primarily focused on biologics can get away with a late-stage pipeline consisting mostly of label expansions, like Genentech (NYSE: DNA) and the several million studies it's testing Avastin in, because it doesn't have to worry as much about generic competitors. Unfortunately, Pfizer is not such a drugmaker and needs new molecules on the market to compensate for its marketed drugs facing patent expiration.

And that's the rub with Pfizer; the level of pipeline innovation that it needs to continuously generate new growth for its top line is unprecedented. Pfizer isn't a badly run drugmaker. Rather, it's suffering from the inevitable and enviable consequences of developing many of the world's best-selling drugs and then having to watch generic compounds take their place. Unlike other Fools, I see Pfizer as more of a value trap than a value play.

"Cigar-butt stocks," as Ben Graham calls them, and stocks with declining top-line sales can definitely make excellent investment opportunities at the right price, but in the words of the famous analyst Happy Gilmore, "the price is wrong" right now with Pfizer.

Guidance from Pfizer is for another year of flat to declining sales, with operating cash flow up only marginally from its 2006 levels. I don't know about you, but I usually prefer a little growth in my stocks, even if Pfizer could afford to bulk up the dividend another 50% right now, given the amount of free cash flow it's generating (that won't be possible four years from now).

I'm not sure what the sound of billions of dollars of drugs going off patent sounds like, but from now until the end of 2012, we'll get to find out as Pfizer loses patent protection on many of its top drugs, including Viagra and Lipitor. With so many other pharmas out there with fewer problems and better growth prospects such as Gilead Sciences (Nasdaq: GILD), even a 5% dividend yield isn't enough to get me excited about Pfizer.

If you agree that Pfizer's chances of making it big in 2008 are as good as Wayne Gretzky making it on the PGA tour, join me in marking Pfizer as an underperform in CAPS. Then come back next week, and we'll let you know who you picked as the worst stock for 2008.

Fool contributor Brian Lawler does not own shares of any company mentioned in this article. GlaxoSmithKline is an active Income Investor pick. Pfizer is an active Inside Value pick. The Fool has an A-plus disclosure policy.