Over the past year or so, Gilead Sciences (NASDAQ:GILD) has gone from Wall Street darling to a battleground stock. This sharp turn in investor sentiment has centered on the company's controversial and record-breaking hepatitis C franchise, composed of the multigenotype treatment Sovaldi, and the once-daily combo pill Harvoni, indicated for genotype-1 patients. 

Source: Gilead Sciences.

Although these two drugs have helped to more than double Gilead's annual revenue, the Street has questioned the franchise's long-term viability because of pricing issues and the potential introduction of newer drugs with even shorter treatment periods (possibly four to six weeks, compared with eight to 12 weeks for current treatments).  

Because payers haven't been exactly thrilled at the prospect of paying $1,000 per pill for Sovaldi, AbbVie (NYSE:ABBV) was able to cut a multi-year deal with leading pharmacy benefits manager Express Scripts (NASDAQ:ESRX) for its genotype 1 offering Viekira Pak. This deal rocked Gilead's shares, causing them to drop by close to 20% over a two-day period. 

Since then, Gilead's shares have rebounded nicely, but serious concerns have swirled around the company's valuation going forward. Simply put, a tug of war has broken out between those who now view Gilead as a so-called value trap, compared with others who believe the stock is cheap on a forward-looking basis. 

My view is that Gilead remains a top-notch stock to buy and hold for the long term, despite these headwinds. Here's why.

Sovaldi beat its competitors to the punch -- that's not an accident
One of the biggest reasons Sovaldi was able to achieve its record-breaking launch was that it was essentially the first "terminator" hepatitis C drug to reach the market, beating Bristol-Myers Squibb's (NYSE:BMY) offering by 10 months and AbbVie's by a year. Although Johnson & Johnson's (NYSE:JNJ) Olysio effectively came out at the same time, it was never meant to be a competitor, but rather a complementary drug to Sovaldi, allowing Sovaldi to rack up sales in quite literally unprecedented fashion.

The point is that Gilead didn't grab the lion's share of the hep C market by happenstance. In 2011, CEO John Martin made the risky decision to spend the bulk of the company's free cash ($11.2 billion, to be exact) on acquiring Pharmasset for the experimental compound that would become Sovaldi, and later on a critical component of Harvoni. By doing so, he procured the most promising hep C drug to date and was able to get it to market well ahead of its rivals. 

But Martin's prowess at identifying powerful new drugs isn't limited to Sovaldi or even the realm of hep C. Through a dozen acquisitions during his tenure, he has been able to grow the company's core HIV franchise in dramatic fashion with the advent of its four-in-one combo pill Stribild, and push Gilead into the high-margin oncology market with its blood-cancer drug Zydelig. 

Newer acquisitions could lead Gilead to become a major player in high-dollar liver disease (not including hep C) down the road as well.

This chart shows why Gilead belongs in your portfolio
My faith in Gilead's long-term future is based on the company's stellar management team, headed by Martin. Since taking the reins as CEO roughly 20 years ago, Martin's business strategy has led to, well, this:

GILD Chart

That's a freakishly amazing record of long-term performance -- one that turned Martin into a billionaire and made his shareholders a whole lot of money over the years.

The bottom line is that the fears over Gilead's hep C market share are overblown. Management has proved its acumen at finding stunning new growth opportunities, time and again. 

As this trend is unlikely to change so long as Martin remains the CEO, I see no reason to sell my Gilead shares. In fact, I've been buying more on the recent dip.