The stock market in general had a pretty good year in 2014, but not all stocks did so well. Here are three stocks that dropped in 2014 that our analysts feel could be ready for a comeback.

Leo Sun: I believe that GlaxoSmithKline (NYSE:GSK) is an undervalued stock which could bounce back in 2015. GSK fell 17% this year due to falling sales of Advair, the weak debut of its two respiratory drugs, a bribery probe in China, and a stunning swap of its high-growth oncology unit for Novartis' low-growth vaccine one.

GSK is now one of the cheapest big pharma stocks, with a trailing P/E of 16, and it pays a hefty forward annual dividend yield of 5.3%.

Looking ahead, GSK plans to reduce annual costs by $1.6 billion within three years. This includes 900 projected job cuts in the U.S., the restructuring of its businesses, and a possible IPO for its stake in ViiV Healthcare, its majority-owned HIV joint venture with Pfizer and Shionogi. GSK's controversial swap of its oncology unit is, in my opinion, logical, since its cancer drugs portfolio (which includes the melanoma treatments Tafinlar and Mekinst) wasn't a market leading one. Therefore, swapping out a roller coaster of "potential" cancer blockbusters for the slow and steady growth of vaccines reduces research and development costs while stabilizing its bottom line for income investors. It also allows GSK to tightly focus its R&D budget on respiratory and HIV drugs.

GSK certainly has a lot to prove after its dismal performance in 2014, but I still think that there's more upside than downside potential for the stock next year.

Dan Caplinger: Las Vegas Sands (NYSE:LVS) has suffered greatly in 2014, with the stock having lost about a third of its value since the beginning of the year. The biggest reason for the casino giant's decline is that revenue in the Asian gaming capital of Macau has fallen sharply, with particularly big drops in the amount of VIP business that casinos there are generating. Given how important Macau has been to the gaming industry overall, Las Vegas Sands and its peers are all shuddering at the potential loss of growth in the key Asian market.

Nevertheless, I think fears about Las Vegas Sands are overblown. Replacing VIP junkets with mass-market customers might take time, but it could also improve Las Vegas Sands' profitability, with more traffic to ancillary services like shopping and entertainment. Moreover, Sands has the potential for growth elsewhere in Asia, especially as Japan considers opening up its market to gambling and as other areas, like South Korea, look at the tourism potential for resorts of their own. Even if Las Vegas Sands suffers a short-term slowdown in earnings growth for the rest of this year and next, investors who take the opportunity to buy in at current low prices could get a huge payoff assuming Macau avoids the worst-case scenarios investors fear.

George Budwell: After rising almost 300% in 2013, shares of CellDex Therapeutics (NASDAQ:CLDX) are down 25% year-to-date. Investors have soured on this name largely because of doubts over the company's lead clinical candidate rindopepimut, indicated for a difficult to treat form of brain cancer (glioblastoma multiforme). The intriguing part, though, is that this pessimism stems from the disease itself, not rindopepimut. Because numerous other experimental drugs have failed to show a clinical benefit in gliobastoma, Mr. Market is assuming the worst for rindopepimut.

Adding to CellDex's misfortunes, the company's other advanced clinical candidate, Glembatumumab vedotin, is an antibody drug conjugate, or ADC. With new classes of cancer treatments, like PD-1 and CDK4/6 inhibitors, showing promise in clinical trials, the Street has started to doubt the future of ADCs in general.

I think these concerns are overblown. Big Pharma is still investing heavily in ADC research, showing that they think this is an important avenue to explore. And indeed, Roche's ADC, Kadcycla, has proven to be a vital tool in the fight against breast cancer. Regarding rindopepimut, I see it as a long-shot, but one with staggering upside potential given the need for effective treatments for gliobastoma.

All told, CellDex's $1.6 billion market cap doesn't appear to adequately reflect the value of even its ADC pipeline, much less rindopepimut -- potentially setting this stock up for a huge comeback in 2015.

Dan Caplinger has no position in any stocks mentioned. George Budwell has no position in any stocks mentioned. Leo Sun owns shares of GlaxoSmithKline and Pfizer. The Motley Fool recommends Celldex Therapeutics. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.