Big pharma stocks have been longtime favorites among investors for several reasons. The fact that they're big means that that they generate huge cash flow, which typically translates to attractive dividends. And big pharma companies operate in a growing industry, with demand for prescription drugs continuing to rise -- especially with expanding elderly populations across the world.

Some big pharma stocks particularly stand out from the crowd. I'd put AbbVie (NYSE:ABBV), Johnson & Johnson (NYSE:JNJ), and Pfizer (NYSE:PFE) at the top of the list. Here's why these are three big pharma stocks you can buy now and hold for years to come.

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AbbVie

There's a lot for investors to like about AbbVie. For starters, the drugmaker's dividend currently yields 3%. Since being spun off from Abbott Labs in 2013, AbbVie has increased its dividend by a whopping 77.5%. And there's plenty of room for more dividend hikes, with the company using 60% of earnings to fund the dividend program.

AbbVie's ability to pay such an enticing dividend stems from its enormously successful product lineup. Humira is on track to rake in over $18 billion in 2017. AbbVie thinks the autoimmune drug will generate close to $21 billion by 2020. A threat from biosimilar rivals to Humira is also much less worrisome after the company struck a deal with Amgen that keeps Amjevita, its Humira biosimilar, off the U.S. market until early 2023. 

The hottest drug for AbbVie right now, though, is Imbruvica. Sales for the cancer drug soared more than 41% year over year in the first three quarters of 2017 and are on pace to reach around $2.5 billion for the full year. That's just AbbVie's portion; Johnson & Johnson co-markets Imbruvica with AbbVie.

Hepatitis C is another area that should be increasingly lucrative for AbbVie. Although sales have dropped for the company's hepatitis C virus (HCV) franchise so far in 2017, the U.S. Food and Drug Administration granted approval for pan-genotypic HCV drug Mavyret in August. 

AbbVie also appears to be poised for strong growth in the coming years thanks to its deep pipeline. The company currently awaits regulatory approval for elagolix for management of endometriosis. The potential blockbuster drug is in a late-stage study targeting treatment of uterine fibroids as well. 

Several other late-stage candidates also hold the potential to become huge winners for AbbVie. Cancer drugs Rova-T and Venclexta are high on that list, as are autoimmune disease drugs risankizumab and upadacitinib. 

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Johnson & Johnson

Johnson & Johnson's dividend yield of 2.37% isn't as high as AbbVie's. And its dividend hasn't grown as fast as AbbVie's has, either. But few companies in any industry can claim the impressive track record of dividend hikes that J&J has, with 55 consecutive years of dividend increases. The likelihood of Johnson & Johnson keeping that streak going seems to be quite good. The company uses roughly 55% of its earnings (and less than half of its free cash flow) to pay out dividends. 

While J&J ranks as a big pharma stock, it's also a leader in consumer healthcare products as well as a major medical device maker. The company's consumer segment is on track to generate sales of close to $13.5 billion this year, while its medical device business should bring in revenue topping $26 billion in 2017.

Still, Johnson & Johnson makes most of its money from its pharmaceutical business. The segment is also poised to be J&J's largest growth driver in the future. Although the company faces competitive pressures for its top-selling drug, Remicade, it also continues to enjoy strong growth for several current products, including Darzalex, Imbruvica, and Stelara.

More growth is coming from J&J's business development efforts. Earlier this year, the company acquired Swiss drugmaker Actelion. This deal allowed J&J to pick up Actelion's pulmonary hypertension franchise, which includes three currently approved drugs. 

Like AbbVie, Johnson & Johnson also has a pipeline ranked in the top five among all big pharma companies. Quite a few of J&J's late-stage programs target additional indications for already-approved drugs. However, the company also claims several promising new candidates, including prostate cancer drug apalutamide and antidepressant esketamine. 

Pfizer

If you're looking for a mouth-watering dividend yield, Pfizer could be right up your alley. The big drugmaker's dividend currently yields around 3.6%. That dividend appears to be pretty safe as well, with Pfizer using only 57% of its free cash flow to fund the dividend program. 

Pfizer's product lineup includes eight blockbusters. Leading the way is the company's pneumococcal vaccine Prevnar 13. However, Pfizer's top drugs with the fastest sales growth are blood thinner Eliquis, breast cancer drug Ibrance, and rheumatoid arthritis drug Xeljanz. These three drugs typify how Pfizer will likely grow in the future. The company partners with Bristol-Myers Squibb on Eliquis. Pfizer picked up Ibrance from its acquisition of Warner-Lambert in 2000. It developed Xeljanz in house.   

The company does face headwinds for its legacy drugs, though, and for some of its drugs that have either recently or soon will lose exclusivity. These drugs are part of Pfizer's essential health segment, which also includes sterile injectables and biosimilars gained from its acquisition of Hospira in 2015. There is some potential good news, however: Pfizer CEO Ian Read has stated that the negative impact from the legacy drugs will decrease in the coming years. 

What about Pfizer's pipeline prospects? They appear to be pretty good. The company awaits regulatory approval for 10 programs and has another 28 late-stage clinical programs. Among Pfizer's top late-stage candidates are pain drug tanezumab and cancer drug Bavencio (which is co-developed with partner Merck KGaA).

Pfizer announced recently that it is evaluating strategic options for its consumer healthcare business. Those options include selling or spinning off the unit, as well as keeping it within Pfizer. Investors stand to win if the company chooses to sell or spin off the consumer business.

Best pick?

I like all three of these big pharma stocks. My favorite, though, is AbbVie. The stock has pretty much everything an investor looks for -- a solid dividend, great growth prospects, and an attractive valuation.

In my view, the biggest knock against AbbVie is its heavy dependence on Humira. However, the company seems to have secured several more years of growth for its top drug. That should give AbbVie plenty of time for Imbruvica and Mavyret to grow revenue and for its pipeline candidates to flourish. I think AbbVie is the best big pharma stock of all right now.  

Editor's note: A previous version of this article incorrectly identified Xeljanz as a drug for treating prostate cancer. The Fool regrets the error.

Keith Speights owns shares of AbbVie and Pfizer. The Motley Fool owns shares of and recommends Johnson & Johnson. The Motley Fool has a disclosure policy.